REESE  LIBRARY 

OF  THK 

UNIVERSITY  OF  CALIFORNIA. 


,190 
Accession  No.       .Q  1.5.4.4...  •   Cla&sNo. 


SELECT  METHODS 


FOOD  ANALYSIS 


HENRY  LEFFMANN,  A.M.,  M.D. 

'  i 

PKOFESSOK  OF  CHEMISTRY  AND  TOXICOLOGY  IN  THE    WOMAN  S    MEDICAL   COLLEGE   OF    PENNSYL- 
VANIA;    PRESIDENT  OF  THH  FACULTY  OF  THE  WAGNER  FREE  INSTITUTE  OF   SCIENCE; 
VICE-PRESIDENT  OF  THE  (BRITISH)   S'  CIETY  OF  PUBLIC  ANALYSTS 


AND 


WILLIAM  BEAM,  A.M.,  M.D. 

FORMERLY    CHII'F    CHEMIST    BALTIMORE    AND    OHIO    RAILROAD 


WITH  FIFTY-THREE  ILLUSTRATIONS  IN  THE  TEXT, 
FOUR    FULL-PAGE    PLATES,    AND    MANY    TABLES 


PHILADELPHIA 

P.    BLAKISTON'S   SON    &    CO. 

1012  WALNUT  STREET 

1901 


V 


Copyright,  1901, 
BY  P.  BLAKISTON'S  SON  &  CO. 


PRESS  OF  WM.  F.  FELL  &  Co.. 

I22O-24  SANSOM   ST., 

PHILADELPHIA. 


PREFACE 


This  book  is  intended  to  be  a  concise  summary  of  analytic 
methods  adapted  to  the  needs  of  both  practising  analysts  and 
advanced  students  in  applied  chemistry.  A  knowledge  of  the 
principles  of  chemistry  and  of  ordinary  laboratory  manipula- 
tions is  assumed,  but  some  physical  and  chemical  methods 
have  been  described  in  detail  to  assist  in  securing  uniformity 
of  operation. 

Much  valuable  matter  relating  to  food  analysis  has  been 
published  in  this  country  within  the  last  decade,  but  most  of 
it  is  scattered  through  official  bulletins  and  reports  that  appear 
in  limited  editions  and  are  distributed  unsystematically.  The 
bulletins  of  the  United  States  Department  of  Agriculture  and  of 
the  Association  of  Official  Agricultural  Chemists  are  now  nearly 
all  out  of  print  and  scarce.  The  present  work  contains  a 
large  amount  of  the  data  and  processes  given  in  those  publi- 
cations, together  with  data  from  reports  of  some  of  the  state 
agricultural  experiment  stations.  The  pages  of  The  Analyst 
have  been  drawn  upon  largely,  as  also  the  works  of  A.  H. 
Allen,  H.  Droop  Richmond,  and  Charles  A.  Mitchell. 

The  collection  and  arrangement  of  material  were  begun 
over  a  year  ago,  but  were  suddenly  interrupted,  and  when 
resumed  after  considerable  time,  it  was  found  necessary  to  in- 
corporate many  new  processes  and  analytic  results.  Dr. 
Beam  having  taken  up  residence  in  a  distant  part  of  the  world, 
the  duty  of  completing  the  book,  as  well  as  the  proof-reading 
and  indexing,  devolved  entirely  upon  the  senior  author.  It 

91544 


VI  PREFACE 

has  been  impracticable  to  keep  Dr.  Beam  advised  of  changes 
or  progress  in  the  work  or  to  submit  any  proof-sheets  to  him. 

The  effects  of  food  adulteration  and  the  methods  of  control- 
ling it  have  not  been  given  any  consideration,  it  being  con- 
sidered that  these  topics  are  not  matters  of  concern  for  the 
analyst.  Special  attention  has  been  given  to  the  presentation 
of  methods  for  detecting  preservatives,  artificial  colors,  and 
poisonous  metals. 

The  plates  of  leaves  and  starch  granules  were  reproduced 
from  Bulletin  13  of  the  United  States  Department  of  Agricul- 
ture, the  originals  being  in  many  cases  retouched  by  Dr.  Beam. 
Several  tables  for  general  reference  have  been  prepared. 
Effort  has  been  made  to  maintain  throughout  the  book  uni- 
formity of  nomenclature  and  method  of  statement  in  describ- 
ing analytic  operations. 

Unless  otherwise  stated,  all  temperatures  are  centigrade 
and  all  readings  of  scale  or  arc  positive. 

715  WALNUT  ST.,  PHILADELPHIA,  PA. 
April,  i go  i. 


CONTENTS 


ANALYTIC  METHODS 

PHYSICAL  DATA:  PAGE 

Specific  Gravity — Melting  and  Solidifying  Points — Boiling  point 
— Polarimetry — Spectroscopy — Microscopy, 9~35 

(  HI  MICAL  DATA: 

Wa'er  and  Fixed  Solids  (Extract) —Nitrogen — Crude  Fiber — 
Ash — Extraction  with  Miscible  Solvents — Extraction  with  Im- 
miscible Solvents — Distillation  and  Sublimation — Apparatus  and 
Chemicals 36-67 

APPLIED  ANALYSIS 
GENERAL  METHODS : 

poisonous  Metals — Colors — Preservatives, 68-91 

SPECIAL  METHODS: 

Starch — Flours    and    Meals — Bread — Leavening    Materials — 

Sugars — Honey — Candies  and  Confections, 92-140 

Fats  and  Oils  :  lodin  Number — Volatile  Acids— Saponification 
Value — Acid  Value — Solubility  in  Acetic  Acid — Thermal  Reac- 
tion with  Sulfuric  Acid — Specific  Temperature  Reaction — 
Bromin  Thermal  Value — Elaidin  Test — Index — Soluble  and 
Insoluble  Acids — Cholesterol  and  Phytosterol — Acetyl  Value 
— Unsaponifiable  Matter — Analytic  Data — Special  Tests,  .  .  .  140-171 
Olive  Oil— Cottonseed  Oil — Maize  Oil— Arachis  Oil — Sesame 
Oil — Rape  Oil — Coconut  Oil — Cacao-butter — Lard — Butter- 
fat,  171-191 

Milk  and  Milk  Products:  Milk— Condensed  Milk— Butter- 
Cheese— Fermented  Milk  Products, 192-250 

Non-alcoholic  Beverages:  Tea — Coffee — Cacao, 251-282 

Condiments  and  Spices  :  Vinegar — Pepper — Long  Pepper — 
Cayenne  Pepper — Ginger — Nutmeg— Mace — Allspice — Cinna- 
mon— Cloves — Mustard — Vanilla  Extract — Lemon  Juice  and 
Sirup — Catsup — Table  Accessories, 283-325 


Vlll  CONTENTS 

SPECIAL  METHODS  (Continued']  :  PAGE 

Alcoholic  Beverages;  Cider — Spirits — Whiskey — Brandy — Gin — 
Rum — Malt  Liquo's —Wine — Alcohol  Tables — Malt  Extracts,  .  326-360 

Flesh  Foods  :  Meats — Meat-extracts, 360-369 

Appendix  :  Addenda — Specific  Gravity  of  Water — Conversion 
Table  for  Thermometric  Degrees — Elements,  Symbols,  and 
Atomic  Weights,  . 37°-375 


PLATES. 

REFERENCES. 

INDEX. 


CORRECTIONS 

Page  135  line  3  from  bottom,  insert  18  after  "  alcohol. 
"     *38    "    5  5  delete  the  reference. 
"     237     "    14,  insert  "seepage  370." 
"     239    "     1 8,  insert  "see  page  371." 
"     294    "     15,  for  "65  "  read  "6.5." 


,-       OF  THE 

UNIVERSITY 

OF 


FOOD    ANALYSIS 


ANALYTIC  METHODS 

PHYSICAL  DATA 

Specific   Gravity. 

In  food  analysis,  determination  of  specific  gravity  of  solids  is 
rarely  made.  Fats  are  usually  tested  in  the  melted  condition. 

The  following  method  for  solid  fats,  due  to  Hager,  is  suita- 
ble for  small  amounts  of  material  :  The  sample  is  melted  and 
allowed  to  drop  slowly  from  the  height  of  about  3  centimeters 
into  some  cold  alcohol  in  a  dish.  The  globules  thus  obtained 
are  placed  in  diluted  alcohol  at  15.5°,  the  strength  of  which 
is  so  adjusted  that  the  globules  float  in  any  part  of  the  liquid. 
The  specific  gravity  of  the  liquid  is  then  determined  ;  it  is,  of 
course,  the  same  as  that  of  the  globules.  Many  substances 
when  cooled  suddenly  are  liable  to  have  abnormal  density, 
hence  it  is  preferable,  as  noted  by  A.  H.  Allen,  to  use  frag- 
ments cut  from  a  solid  mass  cooled  under  normal  conditions 
and  allowed  to  stand  at  least  24  hours. 

The  specific  gravity  of  a  liquid  is  generally  expressed  by 
comparison  with  water.  Confusion  and  inconvenience  have 
arisen  from  the  fact  that  results  have  been  referred  to  water  at 
different  temperatures  as  unity.  It  is  becoming  customary 
to  express,  as  is  proper,  the  temperatures  of  observation  and 

comparison,     ^Jndicates  a  determination  at  100°  and  com- 
2  9 


10 


FOOD    ANALYSIS 


parison  with  water  at   1-5.5°  as  unity.      It  is  best  to  compare 
the  substance  and  the  standard  at  the  same  temperature. 

Pyknonieter  or  Specific-gravity  Bottle. — This  is  a  gener- 
ally applicable  means  of  determining  specific  gravity,  and  is 
capable  of  furnishing  good  results.  It  is  a  bottle — with  a 
perforated  stopper — adjusted  to  hold  a  certain  weight  of 


water  at  a  standard  temperature,  usually  15.5°.  -Bottles  as 
sold  are  often  inaccurate.  The  weight  of  water  that  a  bottle 
holds  should  be  carefully  determined. 

E.  R.  Squibb  devised  a  convenient  form  of  pyknometer  (Fig. 
i)  which  permits  the  determination  to  be  made  at  any  temper- 


SPECIFIC    GRAVITY  I  I 

ature  between  o  and  25°,  and  compared  with  water  at  the 
same  temperature.  As  received  from  the  glass-blower,  the 
chemically  clean  and  tared  bottle  should  hold  100  grams  of 
recently-boiled  distilled  water  at  20°  at  about  58  divisions  of 
a  scale  of  o  to  100.  In  weighing  the  water  into  the  bottle, 
the  fine  adjustment  to  o.ooi  gram  is  made  by  very  narrow 
strips  of  blotting-paper  that  will  pass  easily  down  the  bore  of 
the  graduated  stem  and  absorb  minute  quantities  of  the  liquid. 
When  the  100  grams  are  in  the  bottle,  and  the  column  stands 
between  50  and  65  divisions  of  the  scale,  the  stopper  is  put  in, 
a  leaden  ring  is  put  on  the  neck,  and  the  whole  is  immersed 
in  a  bath  at  o°  until  the  column  of  water  in  the  stem  ceases 
to  fall.  It  should  then  read  at  zero  of  the  scale,  or  not  much 
above  it,  and  the  reading  should  be  noted.  If  it  reads  below 
zero,  the  bottle  is  too  large,  and  the  stopper  part  of  the  stem 
must  be  ground  farther  into  the  bottle  neck,  until  the  reading, 
on  new  trial,  brings  the  column  a  little  above  zero.  The 
bottle  is  then  put  into  a  bath  at  25°  and  kept  there,  with 
stirring  of  the  bath,  until  the  column  ceases  to  rise,  when 
it  should  read  somewhere  from  90  to  100  of  the  scale. 
Should  it  read  above  100,  while  the  lower  limit  is  as  far 
above  the  zero,  the  bottle  is  too  small,  and  the  end  of  the 
stopper  must  be  ground  off  until  the  reading  of  the  column  is 
within  the  graduations  at  both  ends  of  the  scale.  Squibb 
used  the  same  bottle  for  many  years.  During  the  first  two 
years  the  zero  point  rose,  as  happens  in  thermometers,  but 
of  late  years  the  position  has  been  constant. 

Sprengel  Tube. — This  is  a  form  of  pyknometer  with  which 
the  highest  degree  of  accuracy  is  attainable,  and  is  especially 
suitable  for  determinations  at  the  boiling-point  of  water.  It 
consists  (Fig.  2)  essentially  of  a  thin  glass  U-tube  terminating 
in  two  capillary  ends  bent  at  right  angles  and  each  provided 
with  a  ground  cap.  One  of  these  capillary  tubes  must  have 
a  smaller  caliber  than  the  other — not  larger  than  0.25  mm. 


12 


FOOD    ANALYSIS 


The  larger  tube  should  bear  a  mark  at  m.  The  tube  is  filled 
by  immersing  b  in  the  liquid  under  examination,  connecting 
the  smaller  end  with  a  large  glass  bulb,  and  applying  suction 
to  the  latter  by  means  of  a  rubber  tube,  as  shown  in  figure  3. 
If  now  the  rubber  tube  be  closed,  the  glass  tube  will  fill  auto- 
matically. It  is  placed  in  water,  the  ends  being  allowed  to 
project,  and  the  water  is  brought  to  the  proper  temperature. 
A  conical  flask  may  be  used  to  contain  the  water,  the  ends  of 
the  Sprengel  tube  being  supported  by  the  neck.  The  mouth 


FIG.  2. 


FIG.  3. 


of  the  flask  should  be  loosely  covered.  As  the  liquid 
expands  it  will  drop  from  the  larger  orifice.  When  this 
ceases,  the  liquid  is  adjusted  to  the  mark  at  m.  If  beyond 
the  point,  a  little  may  be  extracted  by  means  of  a  roll  ol 
paper.  The  tube  is  then  taken  out  of  the  bath,  'the  caps 
adjusted,  the  whole  thoroughly  dried,  allowed  to  cool,  and 
weighed.  The  same  operation  having  been  performed  with 
distilled  water,  the  calculation  of  the  specific  gravity  is  made 
as  usual. 


SPECIFIC    GRAVITY 

\VistpJial  Balance. — This  affords  a  convenient  means  of 
determining  specific  gravity.  It  consists  of  a  delicate  steel- 
yard provided  with  a  counterpoised  plummet.  The  latter, 
being  immersed  in  the  liquid,  the  equilibrium  is  restored  by 
means  of  weights  or  riders,  the  value  of  which  is  directly 
expressed  in  figures  for  the  specific  gravity  without  calcula- 
tion. Thus,  the  rider  A  is  of  such  a  weight  as  to  express 
the  first  decimal  place,  and  will  be  represented  by  any  of  the 
figures  from  o  to  9  according  to  its  position  on  the  beam. 
Similarly  the  riders  A,  B,  and  C  furnish  the  figures  for  the 


FIG.  4. 

second,  third,  and  fourth  decimal  places  respectively.  The 
weight  A  2  is  used  in  the  case  of  liquids  heavier  than  water. 

According  to  McGill,  the  best  results  are  obtained  by  em- 
ploying plummets  of  different  weights  and  density,  adapted  to 
the  different  characters  (e.  g.,  viscosity)  of  the  liquids  under 
examination.  For  viscous  oils,  the  ratio  of  the  weight  of  the 
plummet  in  air  to  the  weight  of  the  liquid  displaced  should 
be  4  rather  than  the  usual  ratio  (2). 

The  ordinary  form  of  Westphal  balance  is  untrustworthy, 


FOOD    ANALYSIS 


but  good  instruments  are   made  by  some   European   manu- 
facturers. 

The  principle  of  the  hydrostatic  balance  may  be  applied 
by  using  a  plummet  (that  sold  with  the  Westphal  balance 
will  serve)  with  the  ordinary  analytic  balance.  Test-tubes 
weighted  with  mercury  and  sealed  in  the  flame  may  also  be 
used.  The  plummet  is  suspended  to  the  hook  of  the  balance 
by  means  of  a  fine  platinum  wire.  The  specific  gravity  of  any 
liquid  may  be  determined  by  noting  the  loss  of  weight  of  the 


FIG.  5. 


FIG.  6. 


plummet  when  immersed  in  the  liquid  and  dividing  this  by 
the  loss  in  pure  water. 

If  the  determination  be  made  at  the  boiling-point  of  water, 
the  arrangements  shown  in  figures  5  and  6  may  be  employed. 
The  temperature  of  the  liquid  will  not  usually  rise  above  99°. 
This  may  be  done  with  a  hydrometer  or  balance,  if  the  cylin- 
der containing  the  liquid  be  kept  for  a  sufficient  time  in  boiling 
water.  With  the  Sprengel  tube  high  accuracy  may  be  ob- 


SPECIFIC    GRAVITY  t  5 

tained.  The  weight  of  the  Sprengel  tube  and  that  of  water 
contained  at  15. 5°  being  known,  the  tube  should  be  com- 
pletely filled  with  the  oil,  by  immersing  one  of  the  orifices  in 
the  liquid  and  sucking  at  the  other.  The  tube  is  placed  in  a 
conical  flask  containing  water  which  is  kept  actively  boiling,  a 
porcelain  crucible-cover  being  placed  over  the  mouth  of  the 
flask.  The  oil  expands  and  drops  from  the  orifices.  When 
this  ceases,  the  oil  adhering  to  the  outside  is  removed  by  the 
cautious  use  of  filter-paper,  the  tube  removed,  wiped  dry, 
cooled,  and  weighed.  The  weight  of  the  contents  divided  by 
the  weight  of  water  contained  at  15.5°  will  give  the  specific 
gravity  at  the  temperature  attained  compared  with  water  at 
15.5°.  When  the  amount  of  material  is  sufficient,  the  deter- 
mination may  be  made  by  use  of  the  plummet,  employing  a 
cylindrical  bath  with  two  orifices.  One  of  these  is  fitted  with 
an  upright  tube  for  conveying  the  steam  away  from  the  neigh- 
borhood of  the  balance  ;  into  the  other  a  test-tube,  15  cm.  in 
length  and  2.5  cm.  in  diameter,  fits  tightly,  the  joint  being 
made  perfect  by  cork  or  india-rubber.  The  test-tube  is  filled 
with  the  substance  to  be  tested,  and  the  plummet  immersed 
in  it.  The  water  in  the  outer  vessel  is  then  kept  in  constant 
ebullition,  until  a  thermometer,  with  which  the  oil  is  repeat- 
edly stirred,  indicates  a  constant  temperature,  when  the  plum- 
met is  attached  to  the  lever  of  the  balance,  and  counterpoised. 
For  temperatures  higher  than  100°  glycerol  or  paraffin  may 
be  used,  but  considerable  care  is  required  in  such  cases. 

Hydrometers. — These  are  much  used  for  the  determination 
of  the  specific  gravity  of  liquids,  but  the  indications  are  less 
reliable  than  by  the  methods  described  above.  The  instru- 
ments as  furnished  are  rarely  accurately  graduated,  and  the 
zero  point,  at  least,  should  be  verified  by  immersing  in  distilled 
water  at  a  standard  temperature.  Very  sensitive  hydrometers 
with  slender  stems,  and  carefully  graduated,  are  made  for  use 
with  milk.  These  are  capable  of  furnishing  good  results. 


1 6  FOOD    ANALYSIS 

Care  should  be  taken  to  make  the  reading  at  the  top,  center, 
or  bottom  of  the  meniscus  according  to  the  method  used  in 
the  graduation  of  the  instrument.  Instruments  intended  for 
use  with  opaque  liquids  should  be  graduated  to  be  read  at  the 
top  of  the  meniscus. 

The  actual  specific  gravity  of  any  substance  is  the  ratio  of 
its  density  at  a  given  temperature  to  that  of  water  at  the  same 
temperature.  Statements  made  upon  any  other  basis  than  this 
may  be  converted  into  actual  specific  gravity  by  calculation 
from  the  table  of  density  of  water  given  in  the  appendix. 
Thus,  a  determination  of  specific  gravity  of  0.8000  at  ^. 
may  be  converted  into  actual  specific  gravity  (~^)  as  follows  : 

Specific  gravity  of  water  at    15°  =  0.99916. 
"  "  "  100°  —  0.95866. 

100°  100° 

15°  100° 

Therefore,  95866  :  99916   :  :  0.8000  :  0.8337  (actual  specific  gravity  at  100°). 

Melting  and  Solidifying  Points. 

The  determination  of  these  is  often  difficult.  Many  sub- 
stances, especially  fats,  assume  conditions  exhibiting  abnormal 
melting-points,  and  also  frequently  solidify  at  a  temperature 
very  different  from  that  at  which  they  melt.  If,  in  the  prep- 
aration of  any  substance  for  determining  its  melting-point,  it 
is  necessary  to  make  a  previous  fusion,  the  mass  should  be 
allowed  to  rest  not  less  than  24  hours  after  solidification 
before  making  the  experiment.  Chemists  disagree  as  to 
whether  the  melting-point  should  be  considered  to  be  that  at 
which  the  substance  begins  to  be  liquid  or  that  at  which  the 
liquid  is  perfectly  clear.  Ordinary  thermometers  are  fre- 
quently inaccurate,  the  error  amounting  to  a  degree  or  more. 
No  observations  in  which  precision  is  required  should  be 
made  with  unverified  instruments. 

The  following    method  for    determining  melting-points  is 


MELTING    AND    SOLIDIFYING    POINTS 


suitable  for  many  technical  purposes.  By  substituting  strong 
brine  or  glycerol  for  the  water  in  the  bath  observations  may 
be  made  at  temperatures  beyond  the  limits  of  o°  and  100°  : 

The  substance  is  heated  to  a  temperature  slightly  above  its 
fusing-point,  drawn  into  a  very  narrow  glass  tube,  and  allowed 
to  solidify  for  not  less  than  24  hours.  The  tube,  open  at 
both  ends,  is  attached  by  a  wire  or  rubber  ring  to  a  thermom- 
eter so  that  the  part  containing  the  substance  is  close  to  the 
bulb.  The  apparatus,  immersed 
in  water,  is  heated  at  a  rate  not 
exceeding  0.5°  per  minute  until 
fusion  takes  place,  when  the  tem- 
perature is  noted.  The  tempera- 
ture is  allowed  to  fall  and  the 
point  at  which  the  substance  be- 
comes solid  is  also  observed. 
To  insure  uniform  and  gradual 
heatjng,  it  is  necessary  to  im- 
merse the  vessel  containing  the 
thermometer  and  tube  in  an- 
other larger  vessel  filled  with 
water.  A.  H.  Allen  suggests  a 
flask  of  which  the  neck  has  been 
cut  off,  as  shown  in  figure  7.  A 

neater  form  of  apparatus,  from  "  Richter's  Organic  Chem- 
istry," is  shown  in  figure  8  (p.  18). 

The  two  following  methods  are  especially  adapted  to  the 
examination  of  fats  and  waxes.  The  A.  O.  A.  C.  method  dis- 
regards the  abnormal  condition  of  recently-solidified  masses  : 

A.  0.  A.  C.  Method. — A  mixture  of  alcohol  and  water  of 
the  same  specific  gravity  as  the  sample  is  prepared  in  the  fol- 
lowing manner  :  Separate  portions  of  distilled  water  and  95 
per  cent,  alcohol  are  boiled  for  10  minutes.  The  water  is 
poured,  while  still  hot,  into  the  test-tube  described  below 


FIG.  7. 


FOOD    ANALYSIS 


until  it  is  nearly  half  full.  The  test-tube  is  nearly  filled  with 
the  hot  alcohol,  which  is  carefully  poured  down  the  side  of 
the  inclined  tube  to  avoid  too  much  mixing.  If  the  alcohol 


FIG.  8. 


FIG.  9. 


is  added  when  water  is  cold,  the   mixture  will   contain  air- 
bubbles  and  be  unfit  for  use. 

The  apparatus  (Fig.  9)  consists  of:  A  thermometer  reading 
easily  and   accurately  to  tenths  of  a  degree  ;  a  cathetometer 


MELTING    AND    SOLIDIFYING    POINTS  1 9 

for  reading  the  thermometer  (this  may  be  substituted  by  an 
eyeglass  if  held  steadily  and  properly  adjusted)  ;  a  thermom- 
eter ;  a  tall  beaker  35  cm.  high  and  10  cm.  in  diameter  ;  a 
test-tube  30  cm.  long  and  3.5  cm.  in  diameter;  a  stand  for 
supporting  the  apparatus  ;  some  method  of  stirring  the  water 
in  the  beaker  (for  example,  a  rubber  blowing-bulb  and  a  glass 
tube  extending  to  near  the  bottom  of  the  beaker). 

The  melted  and  filtered  fat  is  allowed  to  fall  from  a  drop- 
ping-tube  from  a  height  of  from  i  5  to  20  cm.  on  a  smooth 
piece  of  ice  floating  in  recently-boiled  distilled  water.  Disks 
from  i  to  1.5  cm.  in  diameter,  and  weighing  about  200  mg., 
are  formed.  Pressing  the  ice  under  the  water  the  disks  float 
on  the  surface,  and  are  easily  removed  with  a  steel  spatula, 
cooled  in  the  ice-water  before  using.  The  test-tube  contain- 
ing the  alcohol  and  water  is  placed  in  a  tall  beaker  containing 
water  and  ice,  until  cold.  The  disk  of  fat  is  then  dropped 
into  the  tube  from  the  spatula  and  at  once  sinks  to  the  part 
of  the  tube  where  the  density  of  the  diluted  alcohol  is  exactly 
equivalent  to  its  own.  The  delicate  thermometer  is  placed 
in  the  test-tube  and  lowered  until  the  bulb  is  just  above  the 
disk.  In  order  to  secure  an  even  temperature  in  all  parts  of 
the  alcohol  mixture  in  the  vicinity  of  the  disk,  the  thermom- 
eter is  used  as  a  stirrer.  The  disk  having  been  placed  in  posi- 
tion, the  water  in  the  beaker  is  slowly  heated  and  kept  con- 
stantly stirred  by  means  of  the  blowing  apparatus  already 
described.  When  the  temperature  of  the  alcohol-water 
mixture  rises  to  about  6°  below  the  melting-point,  the  disk 
of  fat  begins  to  shrivel  and  gradually  rolls  up  into  an  irreg- 
ular mass.  The  thermometer  is  lowered  until  the  fat  particle 
is  even  with  the  center  of  the  bulb.  The  bulb  of  the  ther- 
mometer should  be  small,  so  as  to  indicate  only  the  tempera- 
ture of  the  mixture  near  the  fat.  A  gentle  rotatory  move- 
ment should  be  given  to  the  thermometer  bulb.  The  rise  of 
temperature  should  be  so  regulated  that  the  last  2°  of  incre- 


2O  FOOD    ANALYSIS 

ment  require  about  ten  minutes.  The  mass  of  fat  gradually 
approaches  the  form  of  a  sphere,  and  when  it  is  sensibly  so 
the  reading  of  the  thermometer  is  taken.  As  soon  as  the 
temperature  is  taken  the  test-tube  is  removed  from  the  bath 
and  placed  again  in  the  cooler.  A  second  tube,  containing 
alcohol  and  water,  is  at  once  placed  in  the  bath.  The  test- 
tube  (ice-water  having  been  used  as  a  cooler)  is  of  low  enough 
temperature  to  cool  the  bath  sufficiently.  After  the  first  de- 
termination, which  should  be  only  a  trial,  the  temperature  of 
the  bath  should  be  so  regulated  as  to  reach  a  maximum  of 
about  1.5°  above  the  melting-point  of  the  fat  under  examina- 
tion. If  the  edge  of  the  disk  touches  the  sides  of  the  tube 
a  new  trial  should  be  made.  Second  and  third  results  should 
show  a  near  agreement. 

TITER-TEST. — To  eliminate  error  in  determining  melting- 
points  of  intimate  mixtures,  such  as  commercial  fats  and  waxes, 
the  titer-test,  proposed  by  Delican,  has  been  largely  adopted. 

100  grams  of  the  fat  are  saponified,  the  fatty  acids  separated 
by  addition  of  acid,  freed  from  water,  filtered  into  a  porcelain 
dish,  and  allowed  to  solidify  overnight  under  a  desiccator. 
The  mass  is  then  carefully  melted  in  an  air-bath  and  sufficient 
poured  into  a  test-tube  16  cm.  long  and  3.5  cm.  in  diameter 
to  fill  the  tube  a  little  more  than  half-full.  The  tube  is  then 
placed  in  a  suitable  flask,  say  of  2000  c.c.  capacity,  and  a  deli- 
cate thermometer,  indicating  one-fifth  of  a  degree,  inserted  so 
that  the  bulb  reaches  the  center  of  the  mass.  When  a  few 
crystals  appear  at  the  bottom  of  the  tube,  the  mass  is  stirred 
by  giving  the  thermometer  a  rotatory  movement,  first  three 
times  from  right  to  left,  then  three  times  from  left  to  right, 
and  then  continuously,  by  a  quick  circular  movement  of  the 
thermometer,  without  allowing  it  to  touch  the  side  of  the  ves- 
sel, but  taking  care  that  all  solidifying  portions,  as  they  form, 
are  well  stirred  in.  The  liquid  will  gradually  become  cloudy 
throughout,  and  the  thermometer  must  be  observed  carefully. 


BOILING-POINT 


21 


At  first  the  temperature  will  fall,  but  will  soon  rise  suddenly 
a  few  tenths  of  a  degree  and  reach  a  maximum  at  which  it 
remains  stationary  for  a  short  time  before  it  falls  again.  This 
point  is  called  the  "  titer  "  or  solidifying  point. 


Boiling-point. 

For  the  determination  of  boiling-point  the  apparatus  of 
M.  Berthelot  is  convenient.  Figure  10,  from  Traube's 
"  Physico-Chemical  Methods,"  shows  the  construction.  The 
thermometer  is  inclosed  in  an 
outer  tube,  so  that  the  portion  of 
the  scale  to  which  the  mercury  rises 
is  immersed  in  the  vapor.  If  this 
be  not  done,  a  correction  must  be 
applied  for  the  error  produced  by 
the  cooling  of  the  thermometer 
tube.  The  bulb  of  the  thermome- 
ter does  not  reach  into  the  liquid. 
A  few  fragments  of  pumice-stone 
or  broken  clay-pipe  stems  will  pre- 
vent bumping.  The  exit-tube  at 
the  lower  end  of  the  wide  tube 
connects  with  a  condenser.  The 
apparatus  of  O.  Schumann  (Fig. 
1 1)  is  made  entirely  of  glass  and  is 
constructed  on  the  same  principle. 
The  barometric  pressure  must  al-  FIG.  10. 
ways  be  noted  and  allowance  made 

for  the  variation  from  the  standard  pressure,  760  mm.     The 
correction  may  be  made  by  the  following  formula  : 

B  =  B1  -f  0.0375  (76o— P) ;  in  which 
B  is  the  boiling-point  at  normal  pressure, 
B1  the  observed  boiling-point, 
P   the  observed  pressure  in  millimeters. 


FIG.   II. 


22  FOOD    ANALYSIS 

i 

For  an  apparatus  designed  for  special  boiling-point  observa- 
tions see  under  "  Alcoholic  Beverages." 

Polarimetry. 

Polarimeters  are  instruments  used  to  measure  the  extent 
and  direction  of  the  rotation  of  the  plane  of  polarized  light. 
They  consist  essentially  of  a  Nicol's  prism  as  polarizer,  a  tube 
carrying  the  substance  to  be  tested,  and  a  second  Nicol's 
prism,  or  analyzer,  by  which  the  extent  of  rotation  is  meas- 
ured. In  all  forms  some  condition  of  the  field  of  vision 
is  fixed  upon  as  the  zero  point  and  the  rotation  of  the  analyzer 
or  other  manipulation  necessary  to  restore  this  standard  field 
affords  the  measurement  of  the  rotation  caused  by  the  inter- 
posed substance.  Several  types  of  instrument  have  been 
devised,  of  which  two  are  most  important.  In  one  form,  de- 
vised by  Soleil,  white  light  is  used  and  a  colored  field,  known 
as  the  transition  tint,  is  taken  as  the  zero  point.  In  the  other 
type  white  light  or  monochromatic  (yellow)  light  is  used  and 
the  zero  point  determined  by  equalizing  the  brightness  of  the 
field.  Instruments  of  the  first  form  are  unsatisfactory  by 
reason  of  the  difference  in  susceptibility  in  the  eyes  of  differ- 
ent persons  to  color-contrasts.  The  instruments  of  the  second 
type,  commonly  designated  shadow  instruments,  are  now  much 
more  generally  employed  ;  they  have  been  brought  of  late 
years  to  a  high  degree  of  accuracy  and  convenience. 

In  the  Laurent  apparatus,1  shown  in  figure  12,  the  mono- 
chromatic light  passes  through  the  collimating  lens  A  and  is 
polarized  by  the  Nicol's  prism  B,  which  is  so  placed  that  it  may 
be  moved,  on  its  axis,  over  a  small  arc  by  means  of  the  lever 
C  and  clamped  at  any  point  ;  by  this  the  brightness  of  the 
field  may  be  varied  and  the  sensitiveness  of  the  instrument  in- 
creased or  diminished  as  may  be  needed.  The  polarized  beam 
then  passes  through  a  quartz  plate  of  even  thickness,  cut  ex- 
actly parallel  to  the  optic  axis,  and  placed  so  that  it  covers  a 


POLARI METRY  23 

semicircle  of  the  field.  At  the  other  end  of  the  apparatus  is 
the  analyzing  prism  E  and  the  eye-piece  F  fixed  to  a  graduated 
disk.  This  combination  can  be  rotated  upon  its  axis  in  a  com- 
plete circle.  Attached  arms  carry  view-lenses  for  reading  the 
angle  of  rotation,  and  the  instrument  is  set  at  zero  by  an  in- 
dependent adjustment  by  which  the  analyzing  prism  is  rotated 
without  disturbing  the  position  of  the  graduated  disk.  Ver- 
niers are  provided  for  close  measurement.  The  monochro- 


FIG.  23. 

matic  light  must  be  obtained  from  a  sodium  flame,  since  the 
thickness  of  the  quartz  plate  is  adjusted  to  these  rays. 

In  use,  the  tube  is  filled  with  water,  the  instrument  directed 
to  the  source  of  light,  and  the  adjusting  milled  head  turned 
until  the  disk  is  set  at  zero.  The  two  portions  of  the  field 
should  now  appear  equally  illuminated.  If  this  is  not  the  case, 
the  position  of  the  analyzer  must  be  altered  by  means  of  the 
independent  adjustment,  the  index  remaining  undisturbed  at 
the  zero  point.  The  exact  adjustment  to  zero  is  often  tedious, 


FOOD    ANALYSIS 


POLARIMETRY  25 

and  if  desired  a  rough  adjustment  may  be  made,  a  number 
of  readings  taken  and  averaged,  and  the  subsequent  determina- 
tion corrected  accordingly. 

The  tube  is  filled  with  the  liquid  to  be  tested  and  again 
placed  in  the  instrument.  If  optically  active,  the  plane  of  the 
polarized  light  will  be  rotated  and  one-half  of  the  field  of 
observation  will  appear  darker.  The  extent  of  rotation,  which 
will  depend  upon  the  nature  of  the  substance  and  its  amount, 
is  measured  by  rotating  the  analyzer  to  the  right  or  left,  as 
the  case  may  be,  until  the  halves  of  the  field  become  equally 
illuminated.  The  recorded  reading  should  be  the  average  of 
a  number  of  observations,  correction  being  made,  if  necessary, 
for  the  true  position  of  the  zero.  Greater  sensitiveness  is 
attained  by  dividing  the  field  concentrically.  This  is  accom- 
plished by  fastening  a  small  circle  of  quartz  in  the  center  of  a 
glass  diaphragm.  An  instrument  of  this  form  is  now  made 
by  a  Berlin  firm. 

Most  instruments  are  furnished  with  two  scales,  one  express- 
ing angular  degrees  and  the  other  percentage  of  cane-sugar. 
The  latter  registers  100  when  a  given  quantity  of  the  sugar 
has  been  dissolved  in  water  and  made  up  to  100  c.c.  The 
normal  weight  is  given  elsewhere. 

The  above  form  of  Laurent  instrument  can  be  employed  to 
measure  the  rotatory  power  of  all  classes  of  substances,  but 
the  forms  next  to  be  described  give  accurate  indications  only 
with  substances  which  have  the  same  dispersive  power  as 
quartz,  unless  monochromatic  light  be  used.  In  the  Schmidt 
and  Hansch  instrument  (Fig.  13)  the  division  of  the  field  is 
obtained  by  a  special  construction  of  the  polarizing  prism  and 
the  restoration  is  accomplished  by  the  adjustment  of  compen- 
sating quartz-wedges  constructed  so  as  to  produce  in  the  zero 
position  no  rotation.  When  an  optically  active  substance  is 
interposed  in  the  path  of  the  ray,  one  of  the  quartz-wedges 
must  be  moved  to  an  extent  sufficient  to  overcome  this  rota- 
3 


26 


FOOD    ANALYSIS 


tion  in  order  to  restore  the  standard  field.  The  effect  is  de- 
pendent upon  the  fact  that  by  this  movement  the  thickness  of 
the  quartz  is  increased  or  diminished  until  it  compensates  for 


FIG.   14. 

the  rotation  produced  by  the  solution.  The  extent  of  move- 
ment of  the  quartz  is  registered  upon  a  linear  scale,  which  is 
read  by  means  of  a  lens  and  vernier.  White  light  is  employed 


POLARIMETRY 


in  making  the  observations.  A  form  of  the  Laurent  instru- 
ment, with  quartz-wedge  compensation,  and  employing  white 
light,  is  made.  An  instrument  has  been  devised  in  which  the 
field  is  divided  vertically  into  three  zones,  the  central  one 
being  a  broad  band.  Duplicate  Nicol  prisms  are  so  arranged 
that  the  lateral  zones  agree  in  tint,  thus  making  stronger  con- 
trast with  the  central  zone  (Fig.  13). 

It  is  often  desirable,  especially  in  the  examination  of  sugars, 
to  make  the  observation  at  a  temperature  above  the  normal. 
For  this  purpose  the  polarimeter  of  Chandler  and  Ricketts 
may  be  employed.  (Fig.  14.)  The  observation  tube  is  pro- 
vided with  a  thermometer 
and  surrounded  by  water, 
which  may  be  heated  to  the 
desired  point.  Landolt  has 
described  an  improved  form, 
in  which  the  observation  may 
be  readily  taken  at  low  tem- 
peratures. For  a  temperature 
o°  the  tube  is  surrounded  by 
melting  ice.  A  special  feature 
of  the  apparatus  is  an  arrange- 
ment by  which  the  deposition 
of  moisture  on  the  end  glasses  is  prevented.  This  is  accom- 
plished by  providing  a  closed  space  at  each  end  in  which  a 
small  amount  of  calcium  chlorid  is  placed.  The  apparatus  is 
shown  in  figure  15. 

Sources  of  Light. — For  white  light  oil,  gas,  or  electric  lamps 
are  employed,  of  which  numerous  patterns  are  furnished.  Sat- 
isfactory results  may  be  obtained  by  the  Welsbach  lamp. 
H.  W.  Wiley  recommends  the  use  of  the  acetylene  flame, 
especially  for  deeply  colored  solutions. 

For  monochromatic  light  the  lamp  usually  employed  is 
a  Bunsen  burner  with  a  ledge  at  the  top  for  holding  some 


FIG.  15. 


28  FOOD    ANALYSIS 

solid  sodium  compound.  A  fused  mixture  of  sodium  chlorid 
and  phosphate  is  better  than  sodium  chlorid  alone.  The  fol- 
lowing is  an  excellent  method  for  obtaining  a  steady,  strong, 
yellow  light :  Strips  of  common  filter-paper  5  cm.  wide  and 
about  50  cm.  long  are  soaked  in  a  strong  solution  of  sodium 
chlorid  and  thiosulfate,  dried,  and  rolled  into  a  hollow  cylin- 
der of  such  size  as  to  fit  firmly  on  the  top  of  the  Bunsen 
burner.  The  cylinder  is  kept  from  unrolling  by  a  few  turns 
of  fine  iron  wire.  The  flame  burns  at  the  top  of  the  cylinder, 
giving  for  the  first  few  minutes  a  luminous  cone,  but  soon 
becoming  pure  yellow.  The  cylinder  becomes  a  friable 
charred  mass,  but  if  not  disturbed  may  be  used  for  some  time 
continuously  or  at  intervals. 

SPECIFIC  ROTATORY  POWER. — The  specific  rotatory  power 
of  a  substance  is  the  amount  of  rotation,  in  angular  degrees, 
produced  by  a  solution  containing  one  gram  of  the  substance 
in  I  c.c.  examined  in  a  column  one  decimeter  long.  It  is 
usually  represented  by  the  symbol  [a] .  Allen  has  suggested 
the  letter  S  as  more  appropriate.  To  indicate  the  light 
employed  in  the  observation,  SD  or  Sj  is  used.  D  stands  for 
light  of  wave  length  corresponding  to  the  D  line  of  the  solar 
spectrum  (sodium  flame)  and  j  (Jaune)  for  the  transition  tint, 
which  in  the  case  of  sugar  solutions  furnishes  results  corre- 
sponding to  the  "  mean  yellow  ray."  It  is  usual  also  to 
indicate  in  the  same  symbol  the  temperature  of  observation  ; 
thus,  S£. 

Under  ordinary  methods  of  observation  the  specific  rota- 
tory power  is  represented  by  the  following  formula  : 


c          100  a     .        !•  i 
SD  =  — —  ;  m  which 

SD  is  the  specific  rotatory  power  for  the  light  of  the  sodium  flame, 
a  is  the  angular  rotation  observed, 

c  is  the  concentration  expressed  in  grams  per  100  c.c.  of  liquid, 
/  is  the  length  of  the  tube  in  decimeters. 


POLARIMETRV  2Q 

Comparison  of  Scales  of  Various  Instruments. — Polarimeters 
are  usually  provided  with  a  special  scale,  reading  to  100  when 
a  certain  quantity  of  cane-sugar,  called  the  normal  weight,  is 
dissolved  in  water  and  made  up  to  100  c.c.  For  the  German 
instruments,  which  are  largely  used  in  the  United  States,  this 
is  26.048  grams. 

The  instruments  made  by  Schmidt  and  Hansch  are  gradu- 
ated to  read  correct  percentages  when  the  normal  weight  of 
sugar  is  contained  in  100  Mohr's  cubic  centimeters  and  ob- 
served in  a  2  decimeters  tube  at  17.5°.  With  the  Laurent 
apparatus  the  normal  weight  of  the  sugar  should  be  contained 
in  100  true  cubic  centimeters. 

The  volume  of  100  Mohr's  cubic  centimeters  is  that  of 
100  grams  of  water  at  17.5°  weighed  in  air  with  brass 
weights  ;  it  is  equal  to  100.234  true  cubic  centimeters.  For 
the  normal  weight  of  26.048  grams  in  100  Mohr's  cubic  centi- 
meters of  solution,  may  be  substituted  25.9872  grams  in  100 
true  cubic  centimeters  at  17.5°. 

At  the  session  of  the  International  Commission  for  Uniform 
Methods  of  Sugar  Analysis  held  at  Paris,  July  24,  1900,  it 
was  agreed  that  the  normal  weight  shall  be  fixed  at  26  grams 
in  100  true  c.c.  at  20°,  weighed  in  air  with  brass  weights  (see 
under  "  Sucrose  "). 

The  following  factors  may  be  employed  for  the  conversion 
of  data  obtained  by  different  instruments  :  2 

division  Schmidt  and  Hansch  0.3468°  angular  rotation  D. 

D  angular  rotation  D  2.8835  divisions  Schmidt  and  Hansch. 

division  Schmidt  and  Hansch  2.6048  divisions  Wild  (sugar  scale). 

division  Wild  (sugar  scale)  0.3840  division  Schmidt  and  Hansch. 

division  Wild  (sugar  scale)  0.1331°  angular  rotation  D. 

D  angular  rotation  D  °-75II[  division  Wild  (sugar  scale). 

division  Laurent  (sugar  scale)  0.2167°  angular  rotation  D. 

0  angular  rotation  D  4.6154  divisions  Laurent  (sugar  scale). 

Correction  for  Precipitate. — In  some  cases  the  volume  of 
precipitate  produced  by  the  clarifying  agents  is  considerable, 


FOOD    ANALYSIS 


and  a  correction  would  be  necessary.  The  error  may  be 
eliminated  by  Scheibler's  method  :  A  normal  weight  of  the 
sample  is  dissolved  in  water  or  proper  solvent, 'treated  with 
the  clarifying  agent,  the  liquid  made  up  to  100  c.c.,  shaken 
well,  filtered,  and  a  reading  taken  of  the  filtrate.  A  second 
portion  of  normal  weight  is  treated  in  the  same  way  except 

that  it  is  made  up  to  200  c.c.  be- 
fore filtration.  Great  care  must 
be  taken  in  the  readings.  The 
true  reading  is  obtained  by  dividing 
the  product  of  the  two  readings 
by  their  difference. 

Spectroscopy. 

In  practical  analysis  the  spec- 
troscope is  mostly  useful  in  detect- 
ing some  of  the  .rarer  elements 
in  ashes  and  water-residues.  For 
this  purpose  the  direct  vision  in- 
strument shown  in  figure  16  is 
sufficient.  It  will  often  serve  for 
the  examination  of  absorption 
bands,  but  for  precise  research  in 
distinguishing  colors  and  specific 
absorptions  a  more  elaborate  in- 
strument, as  shown  in  figure  17, 

will  be  needed.  Those  now  manufactured  have  either  a  com- 
parison scale  or  the  view-tube  moves  over  a  graduated  arc  so 
as  to  determine  and  record  the  position  of  any  line  or  band. 

For  the  examination  of  ashes  or  water-residues  the  material 
is  mixed  with  a  few  drops  of  hydrochloric  acid,  a  portion  of 
the  mass  taken  up  on  a  loop  of  clean  platinum  wire  and  held 
in  a  non-luminous  flame,  the  spectrum  being  examined  through 
the  instrument.  It  is  important  that  the  first  effects  should 


FIG.  1 6. 


FLUORESCENCE  3 1 

be  noted,  as  some  substances  volatilize  quickly.  The  platinum 
wire  should  be  cleaned  by  dipping  it  in  a  little  pure  hydro- 
chloric acid  and  heating  it  in  the  gas  flame  until  it  imparts  no 
color  thereto. 

For  the  observation  of  absorption-bands  of  liquids,  small 
flat  bottles  with  ground  and  polished  sides  are  used.  These 
permit  the  observation  of  a  thin  or  thick  stratum  as  desired. 
Deeply  colored  solutions  should  not  be  used  since  large  por- 
tions of  the  spectrum  may  be  cut  out  by  general  absorption 
and  the  distinctive  selective  absorption  be  lost. 


FIG.  17. 

For  some  purposes  the  microspectroscope  will  be  needed, 
but  its  use  is  practically  limited  to  medico-legal  work. 

Fluorescence. 

This  may  be  detected  satisfactorily  in  the  manner  described 
by  A.  H.  Allen  :  A  test-tube  or  cylindrical  beaker  is  nearly 
filled  with  a  perfectly  clear  solution  of  the  substance,  set  upon 
a  dark  surface,  and  observed  from  above.  Another  plan  is  to 
make  a  streak  of  the  liquid  on  a  piece  of  black  glass  or  pol- 
ished black  marble  and  examine  this  in  a  good  white  light. 
Tests  can  also  be  made  by  directing  a  ray  of  white  light  from 


32  FOOD    ANALYSIS 

any  source  through  the  side  of  a  beaker  containing  the  liquid 
and  looking  at  it  from  above.  In  all  the  methods  the  liquid 
must  be  perfectly  clear  or  misleading  reflection-effects  are  pro- 
duced. 

Microscopy. 

For  preliminary  examination  of  food  samples  a  hand  lens 
is  useful,  but  the  practical  analysis  involves  the  use  of  the 
compound  microscope.  A  good  instrument  can  now  be  ob- 
tained at  comparatively  small  cost.  It  should  be  supplied 
with  at  least  two  objectives,  one  of  quite  low  power,  about 
13  mm.  focus  (j£  in.),  and  one  of  rather  high  power,  5  mm. 
focus  (i  in.).  For  some  examinations,  especially  for  the 
detection  of  bacteria,  an  immersion-lens  is  needed.  This  is 
costly  and  requires  special  care  in  manipulation.  The  useful- 
ness of  a  microscope  is  much  enhanced  by  the  attachment  of 
a  sub-stage  achromatic  condenser  and  adjustable  diaphragm. 
Polarizing  apparatus  is  needed  especially  for  differentiation  of 
starches. 

The  instrument  shown  in  figure  18  is  of  American  con- 
struction, is  of  moderate  price,  and  arranged  to  receive  all 
accessories.  The  triple  nose-piece,  though  not  necessary, 
is  convenient. 

For  the  better  differentiation  of  objects  submitted  to  ex- 
amination under  the  microscope,  clearing  and  staining  agents 
are  used.  In  many  cases  details  of  structure  are  brought  out 
sharply  by  using  a  dense  liquid  as  a  mounting  fluid.  The 
following  is  a  list  of  the  important  apparatus  and  reagents  : 

Slides  and  cover-glasses. 

Agate  mortar,  2.5  cm.  outside  diameter,  and  a  somewhat 
larger  glass  triturating  mortar  are  useful  for  preparing  mate- 
rials. The  pestles  of  agate  mortars  are  usually  inconveniently 
short,  and  are  much  improved  by  being  mounted  in  a  wooden 
handle. 


MICROSCOPE 


33 


Dissecting  needles  are  easily  made  by  sawing  off  the  metal 
portion  of  an  ordinary  penholder  close  to  the  wood  and  forc- 
ing the  eye-end  of  a  sewing  needle  under  the  ferule  which  has 


FIG.   18. 

been  thus  formed.      Figure  19  shows  a  neat  form  of  a  needle- 
holder  furnished  by  the  instrument  makers. 


FIG.  19. 


34 


FOOD    ANALYSIS 


Small  forceps  and  sharp  scissors  will  be  needed. 

Capped  bottles  provided  with  pipets,  as  shown  in  figure  20, 
are  convenient  for  holding  reagents. 

Watch-glasses  are  used  for  immersing  specimens  in  liquids  ; 
still  better  are  the  Syracuse  glasses,  shown  in  figure  21.  The 
best  form  of  these  has  a  ground-glass  surface  for  entering 
memoranda. 

Water.  Distilled  water  is  best,  but  any  clear,  colorless 
water  not  containing  much  mineral  or  organic  matter  will 
answer. 


FIG.  20. 


FIG.  21. 


GlyceroL     A  pure  article  is  easily  obtained. 

Alcohol.  The  commercial  95  per  cent,  form  is  used  for 
hardening  tissues,  but  for  ordinary  microscopic  work,  a  70 
per  cent,  solution  will  suffice. 

Methyl  alcohol  in  the  purified  form  now  obtainable  may  be 
substituted  in  many  instances  for  common  alcohol. 

Ether,  chloroform,  benzene,  and  carbon  disnlfid  are  occasion- 
ally used  for  their  solvent  action,  especially  to  remove  oils, 
waxes,  and  resins.  For  these  extractions  it  will  often  be 
most  satisfactory  to  operate  in  a  small  continuous  extraction 


MICROSCOPE  35 

apparatus,  with  repeated  washings,  as  described  under  "  Ex- 
traction," and  drying  the  material  at  a  gentle  heat  to  get  rid 
of  all  the  solvent,  which  would  interfere  with  the  action  of 
watery  solutions  or  glycerol. 

CJdoral  hydrate  solution, — a  saturated  solution  in  water. 

Chloral  hydrate  and  iodin  solution, — a  portion  of  the  above 
solution  to  which  a  trace  of  iodin  has  been  added. 

Potassium  iodid  and  iodin  solution, — potassium,  0.4  gram  ; 
iodin,  o.i  gram;  water,  20  c.c. 

Zinc  chloriodid  and  iodin  solution  :  Dissolve  5  grams  of  zinc 
chlorid  and  1.6  gram  of  potassium  iodid  in  17  c.c.  of  water  and 
saturate  with  iodin. 

Sodium  hydroxid, — 5  per  cent,  solution.  In  some  instances 
a  strong  solution  is  employed,  which  is  best  prepared  when 
required. 

Acid  pliloroglucol.  This  is  best  prepared  when  needed  by 
dissolving  a  few  milligrams  in  I  c.c.  of  alcohol  and  adding  a 
drop  of  hydrochloric  acid. 


36  FOOD    ANALYSIS 

CHEMICAL  DATA 

Water  and  Fixed  Solids  (Extract). 

Water  is  usually  determined  with  sufficient  accuracy,  pro- 
vided other  volatile  bodies  are  not  present,  by  heating  the 
material  (in  the  case  of  solids  it  should  be  finely  divided)  in  a 
flat  dish  on  the  water-bath  or  in  the  water-oven  until  it  ceases 
to  lose  weight.  The  residue  constitutes  the  fixed  solids  or 
extract.  Flat  platinum  dishes  from  4  to  8.  cm.  in  diameter 
and  0.5  cm.  high  are  well  adapted  to  this  work.  They  should 
rest  on  porcelain  or  asbestos  rings  when  being  heated.  Nickel 
dishes  are  often  applicable,  especially  the  broad  shallow  cruci- 
ble covers  made  in  dish  form.  Dishes  of  glass,  porcelain, 
and  aluminum  are  less  suitable.  In  many  cases  drying  will 
be  much  facilitated  by  using  an  absorbent  material  such  as 
pure  quartz  sand,  powdered  asbestos,  or  pumice-stone.  These 
materials  should  be  extracted  with  dilute  hydrochloric  acid, 
well  washed,  and  well  dried  before  use.  The  quantity  used 
should  be  rapidly  weighed,  preferably  in  the  dish  in  which  the 
operation  is  to  be  carried  out.  It  is  advisable  to  cover  the 
dish  with  a  nearly  flat,  thin  watch-glass  in  all  the  weighings. 
By  a  few  trials  a  glass  can  be  selected  which  fits  fairly  close 
to  the  rim  of  the  dish  and  restricts  evaporation  or  absorp- 
tion of  water.  It  is  often  convenient  to  weigh  a  small  stir- 
ring-rod with  the  dish  and  absorbent. 

In  many  cases  liquid  can  be  measured  directly  into  the 
dish,  the  residue  being  recorded  in  grains  per  100  c.c.  or 
other  suitable  ratio. 

Sirupy  and  gelatinous  liquids  or  those  containing  much  solid 
matter,  especially  if  this  be  somewhat  difficult  to  dry,  may 
often  be  more  satisfactorily  treated  by  diluting  a  weighed 
portion  with  several  times  its  weight  of  water,  evaporating  a 
measured  or  weighed  amount  of  the  dilute  liquid,  and  calcu- 
lating the  amount  of  residue  in  the  original  substance. 


\\A1KR    AND    FIXED    SOLIDS 


37 


The  ordinary  water-bath  and  water-oven  need  no  descrip- 
tion. The  temperature  of  materials  heated  on  the  former  is 
usually  much  less  than  100°  ;  in  the  latter,  slightly  below 
1 00°.  By  using  strong  brine  a  somewhat  higher  temperature 
may  be  obtained.  In  the  case  of  very  hygroscopic  or  easily 


FIG.  22. 

decomposable  bodies  it  may  be  necessary  to  dry  in  a  current 
of  hydrogen  or  at  reduced  pressure. 

Figure  22  shows  a  drying  oven  for  use  with  a  current  of 
hydrogen.  The  apparatus  was  designed  by  Caldwell  for 
determining  moisture,  ether-extract,  and  crude  fiber  as  pre- 
scribed by  the  A.  O.  A.  C.,  the  three  data  being  determined 
on  the  same  sample. 


38  FOOD    ANALYSIS 

The  bath  is  made  of  copper  and  is  24  cm.  long,  15  high, 
and  8.5  broad.  It  stands  in  a  piece  of  sheet-copper  bent  at 
right  angles  along  the  sides,  as  shown  in  the  end  view  ;  on 
one  side  this  vertical  part  need  not  be  over  I  cm.  high,  just 
enough  to  project  a  little  up  the  side  of  the  bath,  which  rests 
snugly  against  it ;  along  the  other  side  it  projects  upward,  at 
a  little  distance  from  the  side  of  the  bath,  about  15  mm.,  and 
to  about  the  height  of  4  cm.  ;  opposite  each  of  the  tubes  of 
the  bath  a  slot  is  cut  in  this  vertical  part,  which  serves  then  as 
a  shoulder  against  which  the  glass  tube  rests  when  in  place,  to 
keep  it  from  slipping  down  and  out  of  position. 

The  tube  for  containing  the  substance  has  at  the  zone  a 
three  small  projections  on  the  inner  surface,  which  support 
a  perforated  platinum  disk  of  rather  heavy  platinum  foil  carry- 
ing the  asbestos  filter.  This  tube  is  13  cm.  long  and  23  mm. 
inner  diameter,  and  weighs,  with  its  closed  stoppers,  about 
30  grams. 

The  filter  is  readily  made  in  the  same  manner  as  the  Gooch 
filter,  the  tube  being  first  fitted  to  a  suction  flask  by  an  en- 
largement of  one  of  the  holes  of  the  rubber  cork,  or,  better 
still,  by  slipping  a  short  piece  of  rubber  tube  over  it,  of  such 
thickness  that  it  will  fit  tightly  in  the  mouth  of  a  suction  flask 
provided  with  lateral  tube  for  connection  with  the  suction.  A 
thin  welt  of  asbestos  is  sufficient ;  if  it  is  too  thick,  the  gas 
and  ether  will  not  flow  through  readily. 

About  2  grams  of  the  substance  are  put  in  this  tube,  pre- 
viously weighed  with  the  stoppers  b  and  c,  and  the  weight  of 
the  substance  accurately  determined  by  weighing  tube  and 
contents.  The  stoppers  are  removed,  a  band  of  thin  asbestos 
paper  is  wound  around  the  end  d  of  the  tube,  a  little  behind 
the  slight  shoulder  at  the  rim,  as  many  times  as  may  be 
necessary  to  make  a  snug  fit,  when  this  tube  is  slid  down  into 
the  copper  tube  in  the  bath,  thus  preventing  circulation  of  air 
between  the  glass  and  the  copper  tubes  that  would  retard  the 


WAT£R  AND  FIXED  SOLIDS  39 

heating  of  the  former ;  the  stopper  e  is  put  in  the  lower  end 
of  the  tube  for  connection  with  the  hydrogen  supply,  and  the 
stopper  /  in  the  upper  end  ;  this  latter  stopper  is  connected 
by  rubber  tube  with  a  glass  tube  slipping  easily  through  one 
of  the  holes  of  a  rubber  cork  closing  a  small  flask  containing 
a  little  sulfuric  acid,  into  which  this  tube  just  dips  ;  when  as 
many  tubes  as  are  to  be  charged  are  thus  arranged  in  place 
and  the  hydrogen  is  turned  on,  the  even  flow  of  the  current 
through  the  whole  number  is  secured  by  raising  or  lowering 
a  very  little  the  several  tubes  through  which  the  outflow 
passes,  so  as  to  get  a  little  more  back  pressure  for  one,  or  a 
little  less  for  another,  as  may  be  found  necessary.  When  the 
drying  is  supposed  to  be  completed,  the  tubes  are  weighed 
again  with  their  closed  stoppers,  and  so  on. 

For  ether-extraction  the  unstoppered  tube  with  contents  is 
put  directly  into  the  extractor. 

Carr  and  Osborne  have  made  an  extended  series  of  inves- 
tigations as  to  the  determination  of  water,  and  find  that  more 
accurate  results  may  be  obtained  if  the  operation  be  conducted 
under  a  diminished  pressure  at  a  temperature  not  exceeding 
70°  C.  Under  these  conditions  it  was  found  possible  to 
dehydrate  levulose  completely,  without  decomposition.  The 
oven  is  made  of  a  section  of  metal  tubing,  from  15  to  20  cm. 
in  diameter  and  30  to  40  cm.  long.  One  end  is  closed  air- 
tight by  a  brass  end-piece,  brazed  or  attached  by  a  screw. 
The  other  end  is  detachable  and  is  made  air-tight  by  ground 
surfaces  and  a  soft  washer.  On  the  upper  longitudinal 
surfaces  are  apertures  for  the  insertion  of  a  vacuum-gauge 
and  for  attachment  to  a  vacuum-apparatus,  thermostat  and 
thermometer.  The  aperture  for  admission  of  air  or  hydrogen 
is  best  placed  at  the  fixed  end.  The  oven  may  be  heated  by 
a  single  burner,  but  a  series  of  small  jets  extending  along  the 
entire  length  of  the  oven  is  preferable.  The  flame  should 
not  be  allowed  to  strike  the  cylinder  directly ;  the  latter 


4O  FOOD    ANALYSIS 

should  be  protected  by  sheet  asbestos.  The  temperature  of 
the  oven  can  be  kept  practically  constant  by  means  of  the  gas 
regulator,  or  by  attention  to  the  lamp. 

The  method  of  operating  is  as  follows  :  Clean  pumice-stone 
of  two  grades  of  fineness  is  used,  one  that  just  passes  through 
a  i  mm.  mesh  and  one  that  passes  through  a  6  mm.  mesh. 
These  are  digested  with  hot  2  per  cent,  sulfuric  acid,  washed 
by  decantation  until  the  wash-water  is  free  from  acid,  placed, 
wet,  in  a  sand  crucible  and  heated  to  redness.  When  the 
water  is  expelled,  the  material  may  either  be  placed  hot  into  a 
desiccator  or  directly  into  the  drying  dishes.  In  loading  the 
dishes,  place  a  thin  layer  of  the  dust  over  the  bottom  of  the 
dish  to  prevent  the  material  to  be  dried  from  coming  in  con- 
tact with  the  metal ;  over  this  layer  place  the  larger  particles, 
nearly  filling  the  dish.  If  the  stone  has  been  well  washed, 
no  harm  may  result  from  placing  the  dish  and  stone  over  the 
flame  for  a  moment  before  transferring  to  the  desiccator  pre- 
paratory to  weighing. 

If  the  material  to  be  dried  is  dense,  it  is  diluted  until  the 
specific  gravity  is  in  the  neighborhood  of  1.08  by  dissolving  a 
weighed  quantity  in  a  weighed  quantity  of  water.  (Alcohol 
may  be  substituted  in  material  not  precipitable  thereby.)  Of 
this,  2  to  3  grams  may  be  distributed  over  the  stone  in  a  dish 
the  area  of  which  is  in  the  neighborhood  of  20  sq.  cm.,  or  one 
gram  for  each  7  sq.  cm.  of  area.  The  material  is  distributed 
uniformly  over  the  pumice  by  means  of  a  pipet  weighing- 
bottle  (weighing  direct  upon  pumice  will  not  answer),  ascer- 
taining the  weight  taken  by  difference. 

The  dishes  are  placed  in  the  vacuum-oven,  which  should  be 
maintained  at  a  pressure  of  not  more  than  125  mm.  of  mer- 
cury. The  form  of  the  oven  is  not  material  if  the  moisture 
escapes  freely  by  passing  a  slow  current  of  dried  air  beneath 
the  shelf  supporting  the  dishes.  The  temperature  must  not 
exceed  about  70°.  All  weighings  must  be  taken  with  the 


41 

dish  covered  by  a  close-fitting  plate.  The  open  dish  must 
not  be  exposed  to  the  air  longer  than  absolutely  necessaiv. 
Weighings  may  be  made  at  intervals  of  two  or  three  hours. 

In  the  laboratory  of  the  United  States  Geological  Survey  3 
a  sheet-iron  or  nickel  basin  about  10  cm.  in  diameter  and  3 
cm.  deep  is  set  upon  an  iron  plate  which  is  heated  directly  by 
the  burner.  A  platinum  or  pipe-clay  triangle  rests  in  the 
basin  and  supports  the  dish  containing  the  liquid  to  be 
evaporated.  It  is  stated  that  almost  any  liquid  can  be 
evaporated  in  this  way  without  sputtering.  The  temperature, 
however,  is  liable  to  be  too  high  for  many  organic  solutions. 

C.  C.  Parsons  has  obtained  good  results  in  the  drying  of 
sensitive  organic  substances  by  the  following  method :  A 
perfectly  neutral  petroleum  oil,  free  from  animal  or  vegeta- 
ble oils  and  mineral  substances,  sp.  gr.  0.920,  flash  test  224°, 
fire  test  260°,  boiling-point  about  288°,  is  heated  to  about 
1 20°  for  some  time  and  preserved  in  a  well-stoppered  vessel. 
A  quantity  of  oil  about  six  times  that  of  the  weight  of  the 
substance  to  be  dried  is  heated  in  an  evaporating  dish  in  a 
drying  oven  to  a  temperature  of  115°,  and  then  weighed. 
The  weighed  portion  of  the  substance  is  put  into  the  oil  ;  if  it 
be  very  moist,  it  is  added  in  small  portions.  Slight  efferves- 
cence will  usually  occur,  and  the  mass  should  be  kept  in  the 
drying  oven  for  a  short  time  after  effervescence  has  ceased. 
The  evaporating  dish  containing  the  oil  and  substance  is 
weighed  ;  the  loss  is  moisture.  The  whole  operation  may  be 
completed  in  less  than  half  an  hour. 

Nitrogen. 

TOTAL  NITROGEN. — The  Kjeldahl-Gunning  method  is  the 
most  satisfactory. 

The  reagents  and  operation  are  as  follows  : 

Potassium  Sn/fatc.  A  coarsely  powdered  form  free  from 
nitrates  and  chlorids  should  be  selected. 


4-2  FOOD    ANALYSIS 

Strong  Sulfuric  Acid.  This  should  have  a  sp.  gr.  1.84  and 
be  free  from  nitrates  and  ammonium. 

Standard  Acid.  -•  Sulfuric  or  hydrochloric  acid,  the 
strength  of  which  has  been  accurately  determined  by  barium 
chlorid  or  silver  nitrate  as  required. 

Standard  Alkali.  .  —  Ammonium  hydroxid,  sodium  hy- 
droxid,  or  barium  hydroxid,  the  strength  of  which  in  relation 
to  the  standard  acid  must  be  accurately  determined. 

Strong  Sodium  Hydroxid  Solution.  500  grams  should  be 
added  to  5°°  c-c-  of  water,  the  mixture  allowed  to  stand 
until  the  undissolved  matter  settles,  the  clear  liquor  decanted 
and  kept  in  a  stoppered  bottle.  It  will  be  an  advantage  to 
determine  approximately  the  quantity  of  this  solution  required 
to  neutralize  20  c.c.  of  the  strong  sulfuric  acid. 

Indicator.  Cochineal  solution  is  recommended  by  the  A. 
O.  A.  C,  but  methyl-orange  is  quite  satisfactory.  Phenol- 
phthalein  is  not  well  adapted  to  titration  of  ammonium  com- 
pounds. (See  under  "  Indicators.") 

Digestion  Flasks.  Pear-shaped  round-bottomed  flasks  of 
hard,  moderately  thick,  well-annealed  glass,  about  22  cm. 
long,  maximum  diameter  of  6  cm.,  tapering  gradually  to  a 
long  neck,  2  cm.  in  diameter  at  the  narrowest  part,  and 
slightly  flared  at  the  mouth. 

Distillation  Flasks.  Ordinary  flasks  of  about  550  c.c.  ca- 
pacity. A  copper  flask,  such  as  sometimes  used  in  the  manu- 
facture of  oxygen,  may  be  substituted. 

Combined  Digestion  and  Distillation  Flasks.  Hard,  well- 
annealed,  round-bottomed  glass  flasks  with  a  bulb  12.5  cm. 
long  and  9  cm.  in  diameter,  the  neck  cylindrical,  I  5  cm.  long 
and  3  cm.  in  diameter,  flared  slightly  at  the  mouth. 

Condenser  and  Receiver.  A  tube  of  about  I  cm.  caliber 
passes  through  a  rubber  stopper  and  is  cut  off  obliquely  at 
the  lower  end.  This  tube  has  a  bulb  about  4  cm.  diameter, 
the  exit  tube  of  which  is  constructed  so  as  to  prevent  any 


NITROGEN 


43 


liquid  that  may  be  thrown  into  the  bulb  passing  into  the  con- 
densing tube.  The  condensing  tube  is  led  through  a  cooling 
apparatus  and  is  joined  to  another  bulb-tube,  the  lower  end  of 
which  dips  below  the  standard  acid  in  the  receiving  flask. 


FIG.  23. 


FIG.  24. 


The  condensing-tube  should  be  block-tin,  circumference 
about  3.5  cm.,  and  at  least  50  cm.  should  be  in  contact  with 
the  cooling  water.  The  delivery  tube  should  slope  down 
toward  the  flask  and  may  be  connected  flush  with  the  con- 
dcMiser  tube  by  a  close-fitting  rubber  tube,  but  it  will  be  better 


44  FOOD    ANALYSIS 

if  the  tin  tube  is  enlarged  so  as  to  receive  the  glass  for  a 
couple  of  centimeters.  The  lower  end  of  the  condensing 
tube  is  extended  by  means  of  a  glass  tube  and  rubber  con- 
nected or  by  the  attachment  shown  in  figure  23  so  as  to 
lead  the  distilled  liquid  into  the  acid  in  the  receiver.  Many 
operators  arrange  to  allow  the  lower  end  of  the  delivery  tube 
to  dip  below  the  level  of  the  liquid  in  the  receiver.  If  this 
be  done,  the  tube  must  be  provided  with  a  bulb  to  avoid  the 
danger  of  suction  if  the  boiling  happens  to  be  interrupted. 
About  20  c.c.  of  standard  acid  is  placed  in  the  receiver. 

A  special  arrangement  is  shown  in  figure  23.  The  sodium 
hydroxid  solution  is  introduced  through  the  stopcock,  and 
the  distillation  carried  on  by  a  current  of  steam  obtained  from 
the  metal  vessel  which  is  shown  provided  with  a  water-level 
indicator,  a  safety-pipe,  and  a  delivery-pipe.  The  indicator  is 
not  necessary  if  care  be  taken  to  keep  the  boiler  filled  with 
water.  The  safety-pipe  should  pass  nearly  to  the  bottom 
of  the  boiler.  If  obstruction  occurs  in  the  distilling  or  con- 
densing apparatus,  hot  water  maybe  thrown  out  of  the  boiler, 
hence  provision  must  be  made  to  avoid  damage  from  this 
cause.  The  distilling-flask  does  not  need  to  be  directly 
heated. 

Figure  24  shows  a  compact  apparatus  devised  by  H. 
Comer  for  these  distillations,  but  applicable  also  to  other 
similar  operations. 

For  other  distilling  apparatus  see  under  "  Distillation." 

Process. — 0.7  to  3.5  grams,  according  to  the  proportion  of 
nitrogen,  are  placed  in  a  digestion  flask.  Then  10  grams  of 
powdered  potassium  sulfate  and  15  to  25  c.c.  (ordinarily  about 
20  c.c.)  of  the  strong  sulfuric  acid  are  added  and  the  diges- 
tion conducted  as  follows  :  The  flask  is  placed  in  an  inclined 
position  and  heated  below  the  boiling-point  of  the  acid  for 
from  five  to  fifteen  minutes,  or  until  frothing  has  ceased.  Ex- 
cessive frothing  may  be  prevented  by  the  addition  of  a  small 


NITROGEN  45 

piece  of  paraffin.  The  heat  is  raised  until  the  acid  boils 
briskly.  No  further  attention  is  required  until  the  liquid  has 
become  clear  and  colorless,  or  not  deeper  than  a  pale  straw. 
A  small,  short-stemmed  funnel  may  be  placed  in  the  mouth 
of  the  flask  to  restrict  the  circulation  of  air. 

The  flask  is  then  removed  from  the  flame,  allowed  to  cool, 
diluted  with  100  c.c.  of  water  if  the  smaller  form  of  flask  has 
been  used,  the  liquid  transferred  to  the  distilling  flask,  and  the 
digestion  flask  rinsed  with  two  portions  of  water,  50  c.c.  each, 
which  are  also  transferred  to  the  distilling  flask.  With  the 
larger  form  of  flask  the  dilution  is  made  at  once  by  the  cau- 
tious addition  of  200  c.c  of  water.  Granulated  zinc,  pumice- 
stone,  or  0.5  gram  of  zinc  dust  is  added.  50  c.c.  of  the  strong 
sodium  hydroxid  solution,  or  sufficient  to  make  the  reaction 
strongly  alkaline,  should  be  slowly  poured  down  the  side  ot 
the  flask  so  as  not  to  mix  at  once  with  the  acid  solution.  It 
is  convenient  to  add  to  the  acid  liquid  a  few  drops  of  phehol- 
phthalein  solution,  which  will  indicate  when  the  liquid  be- 
comes alkaline,  but  it  must  be  borne  in  mind  that  strong 
alkaline  solutions  destroy  this  indicator.  Connect  the  flask 
with  the  condenser,  mix  the  contents  by  shaking,  and  distil 
until  all  ammonia  has  passed  into  the  standard  acid.  The 
first  150  c.c.  of  the  distillate  will  generally  contain  all  the  am- 
monia, and  should  require  from  40  minutes  to  90  minutes. 
The  distillate  is  titrated  with  standard  alkali  and  the  amount 
of  acid  which  has  been  neutralized  by  the  distillate  calculated 
as  ammonia  or  its  equivalent  in  nitrogen. 

If  nitrates  be  present  in  the  material  to  be  analyzed,  the 
following  modification  in  the  process  must  be  made  :  The 
weighed  material  is  well  mixed  with  35  c.c.  of  sulfuric  acid 
containing  2  per  cent.,  by  weight,  of  salicylic  acid,  and  the 
mass  shaken  frequently  during  ten  minutes ;  5  grams  of 
sodium  thiosulfate  are  added  and  10  grams  of  potassium  sul- 
fate.  The  mixture  is  heated  very  gently  until  frothing  ceases, 


46  FOOD     ANALYSIS 

and  then  according  to  the  usual  method.  The  ammonia  in 
the  distillate  will  include  that  derived  from  the  nitrogen  of  the 
nitrates. 

ALBUMINOID  NITROGEN. — Stutzer's  method  for  this  deter- 
mination requires  a  special  reagent,  as  follows  : 

Copper  Hydroxid  Mixture.  100  grams  of  copper  sulfate 
are  dissolved  in  5000  c.c.  of  water,  25  c.c.  of  glycerol  added, 
and  then  a  dilute  solution  of  sodium  hydroxid  until  the  liquid 
is  alkaline.  The  mass  is  filtered,  the  precipitate  is  mixed  well 
with  water  containing  5  c.c.  of  glycerol  per  1000  c.c.  and 
washed  until  the  washings  are  no  longer  alkaline.  It  is  then 
rubbed  up  with  a  mixture  of  90  per  cent,  water  and  10  per 
cent,  glycerol  in  sufficient  quantity  to  obtain  a  uniform  magma 
that  can  be  measured  with  a  pipet.  The  quantity  of  copper 
hydroxid  per  c.c.  should  be  determined.  It  should  be  kept 
in  a  well-closed  bottle. 

Analytic  Method.  A  suitable  amount  of  the  material,  gen- 
erally about  0.7  gram,  is  heated  with  100  c.c.  of  water  to 
1 00°,  and  a  quantity  of  the  copper  hydroxid  mixture  containing 
about  0.5  gram  of  solid*added,  stirred  well,  allowed  to  cool, 
filtered,  washed  well  with  cold  water,  and  the  filter  and  pre- 
cipitate treated  by  the  Kjeldahl-Gunning  method. 

Substances  rich  in  starch  are  best  subjected  to  about  ten 
minutes'  warming  in  the  water-bath  instead  of  direct  boiling. 
With  substances  containing  much  soluble  phosphates  a  few 
cubic  centimeters  of  alum  solution  should  be  well  stirred  in 
before  adding  the  copper  hydroxid. 

Crude  Fiber. 

The  A.  O.  A.  C.  method,  used  by  many  American  chemists, 
is  substantially  as  follows  :  2  grams  of  the  substance,  well 
extracted  with  ordinary  ether  (see  under  "  Extraction  "  ),  are 
mixed  in  a  500  c.c.  flask  with  200  c.c.  of  boiling  water  con- 
taining 1.25  per  cent,  of  sulfuric  acid,  the  flask  is  connected 


ASH  47 

with  an  inverted  condenser,  the  tube  of  which  passes  only  a 
short  distance  below  the  rubber  stopper  of  the  flask.  The 
liquid  is  brought  to  the  boiling-point  as  rapidly  as  possible 
and  maintained  there  for  30  minutes.  A  blast  of  air  conducted 
into  the  flask  may  serve  to  reduce  the  frothing  of  the  liquid. 
The  mass  is  filtered,  washed  thoroughly  with  boiling  water 
until  the  washings  are  no  longer  acid  ;  the  undissolvep!  sub- 
stance rinsed  back  into  the  same  flask  with  the  aid  of  200  c.c. 
of  boiling  water  containing  1.25  per  cent,  sodium  hydroxid, 
nearly  free  from  sodium  carbonate  ;  again  brought  to  the 
boiling-point  rapidly  and  maintained  there  for  30  minutes  as 
directed  above.  The  liquid  is  filtered  by  means  of  a  Gooch 
crucible  ;  washed  with  boiling  water  until  the  washings  are 
neutral  to  phenolphthalein  ;  dried  at  110°;  weighed  and  incin- 
erated completely.  The  loss  of  weight  is  crude  fiber. 

The  filters  used  for  the  first  filtration  may  be  linen,  glass, 
wool,  asbestos,  or  any  form  that  secures  clear  and  reasonably 
rapid  filtration.  Hardened  filters  may  also  serve.  The  sul- 
furic  acid  and  sodium  hydroxid  are  nearly  N,  and  are  to  be 
made  up  of  the  specified  strength,  determined  by  titration. 

Many  analysts  use  stronger  solutions.  O.  Hehner  uses  5 
per  cent,  acid  and  alkali.  It  would  be  convenient  if  normal 
sulfuric  acid  and  normal  sodium  hydroxid  were  adopted  as 
standards. 

Crude  fiber  should  not  be  called  cellulose. 

Ash. 

The  ash  of  food  materials  may  usually  be  determined  by 
heating  several  grams  in  a  platinum  or  porcelain  crucible  at  a 
low  red  heat.  Higher  temperature  may  cause  loss  of  volatile 
salts — e.  £•.,  chlorids.  If  a  white  ash  cannot  be  obtained  thus, 
the  material  should  be  heated  only  to  a  temperature  sufficient 
to  produce  charring,  the  charred  mass  thoroughly  extracted 
with  water,  and  the  insoluble  matter  collected  on  a  filter, 


48  .          FOOD     ANALYSIS 

which  may  then  be  returned  to  the  crucible  and  ashed.  To 
this  residue  the  filtrate  containing  the  soluble  matter  is  now 
added,  the  liquid  evaporated  to  dryness,  heated  to  low  red- 
ness, cooled,  and  weighed. 

A  muffle,  heated  by  gas,  will  often  be  very  useful  in  the 
incineration  of  organic  bodies.  A  light  draught  of  air  should 
be  maintained  during  the  operation. 

Ash  Soluble  in  Water. — The  ash  obtained  above  is  treated 
with  boiling  water,  the  solution  filtered  through  an  ashless 
filter,  and  the  filter  and  contents  again  ignited  and  weighed. 
The  soluble  ash  is  determined  by  difference.  If  desired,  the 
filtrate  may  be  filtered  to  dryness,  heated  just  below  redness, 
and  weighed.  The  method  first  mentioned  is  the  most  con- 
venient. 

Alkalinity  of  Soluble  Ash. — This  is  determined  by  titrating 
the  soluble  ash  with  standard  acid,  using  methyl-orange  as 
indicator.  The  alkalinity  is  usually  expressed  in  terms  of 
potassium  oxid. 

Ash  Insoluble  in  Acid. — The  residue  insoluble  in  water  is 
treated  with  hydrochloric  acid  and  the  portion  undissolved 
is  well  washed  on  the  filter  with  water,  dried,  ignited,  and 
weighed. 

The  ash  of  fats  is  conveniently  determined  by  the  following 
method  :  A  weighed  quantity  is  melted  in  a  platinum  dish,  and 
a  small  filter,  free  from  ash,  is  folded  in  four,  placed  upright 
in  the  melted  fat,  and  lighted.  The  fat  is  quickly  burnt  off. 

The  following  is  a  compilation  of  various  methods  proposed  for  the  determina- 
tion of  the  ash  of  sugars,  molasses,  honeys,  etc.,  given  by  the  A.  O.  A.  C.  : 

(i)  5  to  10  grams  of  the  material  are  heated  in  a  platinum  dish  of  from  50  to  ico 
c.c.  capacity  at  100°  until  the  water  is  expelled,  and  then-slowly  over  a  flame  until 
intumescence  ceases.  The  dish  is  placed  in  a  muffle  and  heated  at  low  redness 
until  a  white  ash  is  obtained.  If  the  substance  contain  iron  or  any  other  metal 
capable  of  uniting  with  platinum,  a  dish  of  some  other  material  must  be  used. 
For  soluble  ash  the  ash  obtained  as  above  is  digested  with  water,  filtered  through 
a  Gooch  crucible,  washed  with  hot  water,  and  the  residue  dried  at  100°  and 
weighed.  The  difference  of  weights  equals  the  soluble  ash. 


KXTKACTION    WITH     MISCIHLK    SOLVEN  I  >  49 

(2)  To  25  grams  of  molasses  or  50  grains  of  sugar,  50  mg.  of  /inc  oxid  are 
added,  and  the  mass  incorporated  thoroughly  by  adding  dilute  alcohol  and  mix- 
ing.     It  is  then  dried  and  ignited  as  above.      The  weight  of  zinc  oxid  is  deducted 
from  the  weight  of  the  ash. 

(3)  The  mass   is  carbonized  at  low  heat,  the  soluble  salts  dissolved  with  hot 
water,  the   resiilual  mass  burned,  the  solution  of  soluble  salts  added,  and  evapo- 
rated to  dryness  at  100°,  ignited  gently,  cooled  in  a  desiccator,  and  weighed. 

(4)  The  sample   is  saturated   with   sulfuric  acid,  dried,  ignited  gently,  then 
burnt  in  a  muffle  at  low  redness.      One-tenth  of  the  weight  of  the  ash  is  deducted 
to  calculate  the  percentage. 


Extraction  with  Miscible  Solvents. 

Cold  extraction  may  be  made  by  macerating  a  weighed 
portion  of  the  material  in  a  measured  volume  of  the  solvent 
in  a  vessel  closed  so  as  to  prevent  appreciable  evaporation, 
decanting  or  filtering  an  aliquot  portion  of  the  liquid,  evap- 
orating and  weighing  the  residue.  The  time  of  macera- 
tion and  the  method  of  evaporation  must  be  adapted  to 
each  case.  The  percolation  method  of  producing  a  con- 
centrated solution  is  not  well  suited  to  the  operations  of  food 
analysis. 

For  thorough  extraction,  especially  with  difficultly  soluble 
materials  and  volatile  solvents,  the  continuous  extraction  ap- 
paratus devised  by  Szombathy,4  but  commonly  called  the 
Soxhlet  tube,  is  most  suitable.  The  general  construction  and 
arrangement  are  so  well  known  as  not  to  require  detailed 
description. 

The  apparatus,  as  shown  on  page  50,  is  provided  with  a 
globular  metal  condenser,  but  the  ordinary  spiral  condenser 
or  Cribb's  form  may  be  employed.  The  material  may  be 
placed  in  a  fat-free  paper  thimble  and  covered  with  a  plug  of 
cotton  to  prevent  loss  of  fine  particles.  In  place  of  the  cotton 
plug  a  Gooch  crucible  may  be  used,  as  shown  in  the  cut. 
The  top  of  the  thimble  should  be  a  short  distance  below,  and 
the  top  of  the  crucible  a  short  distance  above,  the  bend  of  the 
siphon.  The  thimble  should  be  supported  by  a  section  of 
5 


FOOD    ANALYSIS 


LJ 


glass  tubing,  I  to  2  cm.  long,  with  rounded  edges  ;  the  edge 
on  which  the  thimble  rests  should  be  a  little  uneven  to  pre- 
vent a  close  joint,  which  would  hinder 
the  siphoning  of  some  of  the  liquid. 

Another  method  is  to  use  a  glass 
tube  open  at  both  ends,  the  material  to 
be  extracted  being  held  in  position  by 
loose  plugs  of  cotton  placed  above  and 
below. 

To  obtain  good  results  with  ether  it 
is  essential  that  it  be  as  nearly  as  pos- 
sible free  from  alcohol  and  water.  The 
method  of  purification  recommended  by 
the  A.  O.  A.  C.  is  as  follows  : 

Commercial  ether  is  washed  with  two 
or  three  successive  portions  of  distilled 
water  and  solid  sodium  hydroxid  added 
until  most  of  the  water  has  been  ex- 
tracted. Carefully-cleaned  metallic  so- 
dium, cut  into  small  pieces,  is  added 
until  there  is  no  further  evolution  of 
hydrogen.  The  ether  thus  dehydrated 
must  be  kept  over  metallic  sodium,  and 
should  be  only  lightly  stoppered  in  order 
to  allow  any  accumulated  hydrogen  to 
escape. 

Light    petroleum,   commonly    known 
as    benzin    and    gasolin,    and    often    by 
other  trade-names,  may  be  used  for  ex- 
traction purposes.      It  should  be  purified 
FIG.  25.  by  redistillation,  selecting  the   portions 

which  come  over  below  50°. 

Other  solvents  are  employed  in  special    cases.     Benzene, 
chloroform,  carbon   disulfid,  and  acetone  are  now  obtainable 


TIG.  26. 


FOOD    ANALYSIS 


of  high  purity,  but  are  liable  to  contain  some  moisture,  which 
can  be  removed  by  treatment  with  plaster- of-Paris. 

Knorr's  extraction  apparatus  substitutes  mercury  seals  for 
corks  and  ground  joints.     Several  other  improvements  in  the 
details  of  the  Soxhlet  apparatus  are  made,  as  shown  in  figure 
26.     The  condenser  is  a  tube  with  a  series  of  bulbs,  and  is 
fused  to  the  hood  which  holds  the  material  to  be  extracted. 
The  rubber  stopper  which  supports  the  outside  of  the  con- 
denser should   be  put   on   before   the  junction  is  made.     A 
shows  a  section   of  the  flask  and  lower  part  of  the  hood  in 
position.     5  is  a  siphon  for  preventing 
the  accumulation  of  solvent  between  the 
hood  and  the  neck  of  the  flask.     The 
junction  between  the  hood  and  the  flask 
is  sealed  by  mercury.     The  flask  is  held 
by  a  rubber  band  which  passes  under  it 
and  over  two  hooks  on  the  hood.    Figure 
28  shows  a  tube  for  holding  the  mate- 
rial ;  D  is  a  perforated  platinum  plate. 
At  /  are  nipples    for  holding  the    tube 
upon  the  rim  of  the  flask.     A  convenient 
arrangement  of  the  siphon  is  also  shown 
in  figure  28  ;  the  siphon,  being  within  the 
apparatus,  is  protected    from  breakage. 

With  Knorr's  apparatus  little  leakage  occurs  even  with  the 
most  volatile  solvents. 

For  the  recovery  of  the  solvent  the  apparatus  shown  in 
figure  27  is  used,  in  which  A  is  the  flask  containing  the  liquid. 
C  may  be  a  ground  joint ;  the  joints  of  A  and  B  are  sealed 
with  mercury. 

It  must  not  be  overlooked  that  mercury  seals  exposed  con- 
stantly to  the  air  of  badly  ventilated  rooms  may  cause  chronic 
mercurial  poisoning. 

Wiley's  extraction  apparatus  is  shown  in  figure  29. 


V 


FIG.  28. 


EXTRACTION    WITH     IMMISCIBLE    SOLVENTS 


53 


The  outer  vessel  is  a  stout  glass  tube.  The  inner  vessel  is 
of  nickel-plated  metal  in  a  series  of  double  cones  ;  the  flat 
plate  at  the  top  fits  tightly  on  the  ground  surface  of  the  glass 
vessel.  Cold  water  is  passed  continually  through  the  interior 
of  the  metal  vessel,  by  which  the  solvent  is  constantly  con- 
densed, and  drops  upon  the  material  to  be  treated,  which  is 
contained  in  a  porcelain  or  platinum  bucket,  with  a  detach- 
able perforated  bottom,  through  which  the  extract  drops  into 
a  vase-like  receiver  resting  in  the  outer 
vessels.  This  is  not  shown  in  the  cut,  and 
will  not  be  required  if  the  estimation  be 
made  by  the  indirect  method. 

Extraction  with  Immiscible  Solvents. 

Solvents  not  miscible  with  water  are  em- 
ployed for  extracting  substances  by  shaking 
the  solvent  thoroughly  with  the  aqueous 
solution,  allowing  the  liquids  to  separate, 
and  removing  one  of  them.  The  process 
is  most  conveniently  performed  in  a  stop- 
pered separator.  The  principal  difficulty 
is  the  liability  of  some  liquids  to  form 
emulsions  which  separate  only  after  long 
standing.  Separation  may  sometimes  be 
hastened  by  cooling  the  mixture  or  by 
adding  more  of  the  solvent.  One  of 
the  most  satisfactory  methods  when  operating  upon  small 
amounts  of  liquid  is  to  whirl  the  mixture  for  a  short  time  in  a 
high-speed  centrifuge. 

Figure  30  shows  an  apparatus  devised  by  O.  Forster  for 
use  with  solvents  lighter  than  water. 

The  cylinder  A  should  hold  about  1000  c.c.  Two  openings 
are  not  necessary,  since  both  tubes  may  pass  through  the  cork, 
but  the  arrangement  shown  is  more  convenient.  600  c.c.  of 


FIG.  29. 


54 


FOOD    ANALYSIS 


the  solution  are  placed  in  the  cylinder,  300  c.c.  of  solvent 
added  and  the  mixtures  well  shaken.  The  rest  of  the  appa- 
ratus is  then  attached.  The  flask  B  has  a  capacity  of  200  to 
300  c.c.;  the  solvent  in  it  is  heated  by  a  water-bath.  The 
vapor  passes  by  a  into  b,  the  condensed  liquid  flows  to  the 
bottom  of  A  and  rises  through  the  solution  ;  the  upper  layer 

returns  through  c  into  B.  The 
tube  c  should  not  extend  into  the 
liquid  in  B.  A  small  quantity  of 
aqueous  liquid  may  collect  at  inter- 
vals in  B  and  should  be  removed. 

Distillation  and  Sublimation. 

Retorts  and  alembics  are  now 
but  little  used,  but  are  serviceable 
in  some  cases.  With  glass  vessels 
the  irregular  percussive  boiling, 
commonly  called  "bumping,"  is 
liable  to  break  the  vessel  or  to 
spurt  portions  of  the  undistilled 
liquid  into  the  condensing  appara- 
tus. Bumping  may  usually  be  pre- 
vented by  the  addition  of  a  few  frag- 
ments of  pumice,  clay  pipe,  or  plati- 
num foil.  Dry  pumice  floats  on 
most  liquids.  It  may  be  made  to 
sink  either  by  soaking  it  in  water  for 

a  day  or  so  or  by  heating  the  fragment  to  redness  and  quench- 
ing it  in  the  liquid.  With  inflammable  liquids,  the  latter 
method  must  be  used  cautiously.  A  special  device  to  prevent 
bumping  is  described  by  W.  H.  Hess  and  A.  B.  Prescott  :  5  A 
capillary  tube  is  cut  of  such  length  that  it  cannot  lie  on  the 
bottom  of  the  distilling  vessel,  and  projects  some  distance 
above  the  level  of  the  liquid.  One  end  is  sealed  and  the  tube 


FIG.  30. 


DISTILLATION     AND     SUBLIMATION 


55 


is  placed  with  open  end  resting  about  the  center  of  the  bot- 
tom of  the  vessel. 

In  special  apparatus,  a  flask  with  a  short  platinum  wire 
fused  into  the  bottom  is  preferred.  As  a  protection  against 
spurting,  bulb-tubes  are  used,  as  shown  on  page  43. 

Condensing  apparatus  is  made  in  considerable  variety ; 
practically,  glass  and  block-tin  are  the  only  available  materials 
for  tubes.  Glass  tubes  are  liable  to  crack  at  the  point  at 


FIG.  31. 


which  the  cooling  action  begins.  To  avoid  leakage  and  the 
contact  of  hot  vapors  with  corks  or  rubber  tubes,  the  con- 
nections should  be  as  few  as  possible.  Arrangements  of  dis- 
tilling apparatus  are  shown  in  the  section  on  nitrogen  determ- 
ination and  other  convenient  forms  in  figures  31  and  32.  In 
the  former  a  block-tin  worm  passes  through  a  copper  tank 
containing  the  cooling  water.  The  upward  inclination  of  the 


FOOD    ANALYSIS 


neck  of  the  retort  causes  any  material  that  is  thrown  into  it 
to  return  to  the  boiling  liquid.  This  is  a  convenient  appara- 
tus for  the  so-called  ammonia  process  in  water  analysis. 


FIG.  32. 

Figure  32  shows  an  improved  form  of  distilling  apparatus 
devised  by  R.  S.  Weston.  The  condenser  tube  is  of  copper 
or  japanned  galvanized  iron.  The  details  of  construction  and 


DISTILLATION    AND     SUBLIMATION 


57 


B 


arrangement  are  sufficiently  indicated  in  the  drawing.  The 
apparatus  is  shown  as  arranged  for  water  analysis.  When 
Kjeldahl  distillations  are  being  made  the  lower  end  of  the 
block-tin  tube  should  be  extended  by  means  of  a  bulbed 
glass  tube,  as  noted  elsewhere.  Safety  bulbs  may  also  be 
placed  between  the  flask  and  condensing  tube  in  such  a  way 
as  to  avoid  rubber-tube  connections.  Materials  are  added  by 
means  of  long-stemmed  funnels.  Weston  uses  a  Bunsen 
burner,  but  it  is  probable  that  the  low 
temperature  burner  would  be  satisfac- 
tory in  many  cases. 

Figure  33  shows  Cribb's  condenser, 
which  may  be  attached  to  any  distilling 
apparatus.  The  distillation  tube  is  at- 
tached at  A.  The  walls  are  double ; 
condensation  occurs  in  the  space  between 
them,  and  the  distillate  flows  out  by  the 
tube  E.  The  cooling  water  flows  through 
F  to  the  bottom  of  the  inner  space,  over- 
flows at  J  into  the  catch-basin  below,  es- 
caping by  G.  The  stopper  7  serves  to 
steady  the  tube  F,  and  should  have 
several  large  notches  cut  in  it  to  allow 
the  water  to  escape  freely.  It  is  usually 
necessary  to  wrap  a  piece  of  muslin 
around  the  outside  of  the  apparatus  to  cause  the  overflow- 
ing water  to  run  properly.  The  condenser  may  be  made 
of  glass,  block-tin,  or  tinned  copper.  Experience  shows  that 
the  apparatus  will  be  more  satisfactoiy  if  some  of  the  dimen- 
sions are  changed  from  those  indicated  in  the  figure,  which  is 
taken  from  Cribb's  paper.  The  annular  space  should  be 
larger,  especially  at  the  bottom  ;  the  catch-basin  must  be 
roomy,  and  G  should  have  a  caliber  at  least  three  times  that 
of  F.  The  catch -basin  is  held  in  place  by  rubber  tubing. 


FIG.  33. 


So  FOOD    ANALYSIS 

The  condenser  is  supported  by  a  strong  clamp.  L  is  for 
attachment  of  an  air-pump  for  distillation  under  diminished 
pressure. 

For  forms  and  arrangements  of  reflux  or  inverted  con- 
densers see  under  "  Extraction." 

Distillation  of  small  amounts  of  material  may  be  made 
with  the  ordinary  extractor,  terminating  the  operation  before 
the  distillate  reaches  the  level  of  the  bend  of  the  siphon. 

Distillation  under  reduced  pressure  or  in  a  current  of  indif- 
ferent gas  may  be  carried  out  in  the  apparatus  devised  by 
L.  T.  Thorne, 6  which,  in  a  form  improved  by  F.  C.  Axtell,  is 


FIG.  34. 


shown  in  figure  34.  This  consists  of  a  distilling-flask,  a 
condenser,  an  upright  receiver,  and  a  small  receiving-flask. 
It  is  convenient  to  have  several  of  the  last.  The  distilling- 
flask  is  furnished  with  a  tap-funnel.  Its  mouth  is  best  closed 
with  a  good  cork  which  has  been  well  softened.  .A  ther- 
mometer may  be  passed  through  this.  The  condenser  and 
upright  receiver  are  joined  by  fusion  and  the  latter  has  three 
stopcocks,  the  upper  and  lower  being  of  ordinary  form,  the 
middle  one  a  three-way  cock.  All  stopcocks  and  joints  must 
be  well  ground. 


DISTILLATION    AND    SUBLIMATION 

The  operation  is  as  follows  :  A  little  powdered  pumice- 
stone  is  placed  in  the  distilling-flask  and  the  cork  with  the 
thermometer  placed  in  position.  The  tube  at  the  upper 
extremity  of  the  receiver  is  connected  with  the  air-pump,  a 
strong  vessel,  having  a  capacity  of  several  liters,  being  inter- 
posed between  the  pump  and  the  apparatus  to  obviate  the 
effect  of  sudden  variations  of  pressure.  The  funnel-tap  on 
the  distil  ling-flask  is  closed,  the  upper  stopcock  is  opened 
and  the  lower  one  is  closed,  and  the  middle  one  opened  so  as 
to  exhaust  the  receiving-flask.  The  liquid  is  then  introduced 
into  the  distilling  flask  through  the  tap-funnel,  and  after  the 
foaming  due  to  the  liberation  of  air  by  the  pumice-stone  has 
subsided,  distillation  is  begun.  When  the  first  fraction  or  a 
sufficient  quantity  has  collected  in  the  upright  receiver,  the 
upper  cock  is  closed,  the  lower  one  opened,  and  the  liquid 
allowed  to  run  into  the  receiving-flask.  The  lower  cock  is 
closed  and  the  middle  one  turned  so  as  to  admit  air  to  the 
flask,  which  is  then  disconnected  and  another  substituted. 
The  cocks  are  then  set  for  the  beginning  of  another  distilla- 
tion. 

Axtell  finds  that  powdered  pumice,  used  as  indicated, 
entirely  prevents  bumping. 

For  lubrication  of  glass  stopcocks,  the  following  mixtures, 
devised  by  F.  C.  Phillips,  are  useful  : 

Pure  rubber, 70  parts  Pure  rubber, 70  parts 

Spermaceti, 25     "         or         Unbleached  beeswax,    .  30     " 

Vaselin, 5      " 

The  rubber  must  be  fresh  and  pure  ;  rubber  scraps  will 
not  answer.  It  should  be  melted  in  a  covered  vessel,  the 
other  materials  added,  and  the  mixture  well  stirred  while  hot, 
care  being  taken  not  to  scorch  it.  It  must  not  be  exposed  to 
air  longer  than  is  necessary  during  heating,  and  should  be  kept 
in  well-closed  bottles.  These  mixtures  may  be  removed  from 


60  FOOD    ANALYSIS 

the  parts  of  the  apparatus  which  are  not  easy  of  access  by 
the  use  of  a  little  strong  nitric  acid,  which  loosens  the  lubri- 
cant so  that  it  may  be  washed  out  with  water. 

Fractional  distillation  may  be  performed  with  the  Thorne- 
Axtell  apparatus.  Special  bulb-tubes  have  been  devised  for 
attachment  to  ordinary  flasks  so  that  the  vapor  may  be  par- 
tially condensed  and  succeeding  portions  washed  with  the 
liquid  which  runs  back  continuously  into  the  flask.  Among 
these  are  the  Le  Bel-Heninger  and  Glynsky  tubes.  The 
former  bears  from  two  to  six  bu-lbs.  The  upper  part  has  an 
inclined  side  tube  for  connection  with  the  receiver  and  an 
opening  through  which  the  thermometer  can  be  passed.  Each 
of  the  bulbs  is  connected  with  the  one  just  below  by  a  side 
tube.  At  the  constricted  part  of  each  bulb  a  small  thimble 
of  platinum,  copper,  or  nickel  gauze  rests.  The  vapor  con- 
denses in  the  cups  and  washes  the  vapor  subsequently 
formed.  The  liquid  runs  off  from  each  bulb,  back  to  the 
flask.  The  flame  should  be  regulated  so  as  to  keep  all  the 
cups  full,  and  cause  the  distillate  to  fall  from  the  end  of  the 
tube  in  separate  drops.  In  the  Glynsky  bulb  hollow  glass 
balls  replace  the  gauze. 

It  must  be  borne  in  mind  that  the  present  United  States 
revenue-law  requires  all  distilling  apparatus  to  be  registered, 
no  matter  for  what  purpose  it  is  used.  Heavy  penalties  are 
imposed  for  using  non-registered  stills.  No  fee  is  imposed 
for  registry,  which  is  made  on  blanks  furnished  by  the  Col- 
lector of  Internal  Revenue. 

SUBLIMATION  may  be  performed  in  a  narrow  test-tube  or 
watch-glasses  with  concavities  facing,  the  upper  glass  being 
slightly  small  so  that  it  may  fit  well.  A  gentle  heat  is  ap- 
plied to  the  lower  dish.  By  substituting  a  beaker  containing 
water  for  the  upper  watch-glass  a  better  cooling  effect  will  be 
obtained. 


APPARATUS    AND    CHEMICALS 


6l 


Apparatus   and  Chemicals. 

These  can  now  be  obtained  generally  of  good  quality  at 
almost  all  times  and  places,  but  a  few  suggestions  may  be  of 
value. 

Centrifuge. — Centrifugal  apparatus  is  of  much  advantage  in 
laboratory  work.  The  slow-speed  machines  made  for  milk 
analysis  are  of  limited  application  ;  much  better  results  are 
obtained  by  the  high-speed  apparatus  of 
the  type  shown  in  figure  35. 

In  operating  such  machines,  the  load 
on  the  revolving  arms  must  be  balanced 
or  the  center  of  gravity  will  not  coincide 
with  the  center  of  revolution,  and  an  ob- 
jectionable vibration  will  be  produced. 
The  machine  should  be  attached  to  a  firm 
table  or  shelf  and  kept  properly  oiled  and 
protected  from  dust.  The  tubes  usually 
furnished  are  narrowed  at  the  bottom, 
and,  as  solid  material  is  apt  to  be  packed 
closely  by  the  centrifugal  action,  it  is 
sometimes  difficult  to  dislodge  it,  but 
care  should  be  taken  to  get  all  such  ma- 
terial out  of  the  tube  so  as  not  to  con- 
taminate the  substance  used  in  a  subse- 
quent experiment.  If  it  be  desired  to 
use  vessels  not  narrowed  at  the  base, 

small  glass  tubes  closed  by  cork  at  one  end  may  be  substituted. 
In  this  case,  however,  the  lower  end  of  the  tube-holder  should 
be  packed  with  cotton  to  such  a  height  that  the  cork  cannot 
be  driven  into  a  part  of  the  tube  narrow  enough  to  hold  it 
tightly.  If  this  precaution  be  neglected,  the  rotation  will  push 
the  glass  tube  so  far  into  the  tube-holder  that  it  may  be  impos- 
sible to  draw  it  out  without  leaving  the  cork. 

Glassware  suitable  for  most  laboratory  work  is  now  made 


FIG.  35. 


62  FOOD     ANALYSIS 

in  the  United  States,  but  the  Bohemian  and  Jena  glass  still 
shows  important  merit  which  will  lead  to  preference  for  it  in 
many  cases.  For  the  cleaning  of  glass  and  porcelain,  especi- 
ally when  working  with  fatty  matters,  the  commercial  triso- 
dium  phosphate  is  of  much  use.  Vessels  cleaned  with  it  must 
be  well  rinsed.  A  bath  of  so-called  battery  fluid  (potassium 
dichromate  or  sodium  dichromate,  or,  better,  the  crude  chromic 
acid  sold  for  the  purpose,  250  grams  ;  water,  2000  c.c.;  sul- 
furic  acid,  300  c.c.)  will  make  an  efficient  cleaning  solution  for 
all  non-metallic  articles.  These  should  be  cleansed  with  soap, 
sodium  phosphate,  or  sodium  carbonate  to  get  rid  of  the 
organic  matter,  rinsed,  and  then  soaked  in  the  liquid  overnight. 
The  solution  gives  off  no  fumes  and  its  color  guards  against 
imperfect  rinsing.  It  is  of  little  value  when  it  has  become 
brown  or  green,  but  may  be  freshened  by  adding  crude  chromic 
and  sulfuric  acids.  As  the  liquid  is  very  corrosive,  all  waste 
from  it  should  be  washed  down  the  drain-pipes  with  a  free  flow 
of  water.  Strong  sulfuric  acid  is  used  by  some  chemists, 
especially  for  cleaning  greasy  apparatus.  Organic  matters 
such  as  corks  and  tubes  should,  of  course,  not  be  put  in  these 
cleaning  solutions. 

For  heating  beakers  and  flat-bottomed  flasks  the  hot-plate 
is  much  used,  but  the  thin  cast-iron  plates  commonly  fur- 
nished are  unsatisfactory.  A  better  form  is  a  rolled  plate  at 
least  I  cm.  thick.  Nickel  wire-gauze  is  a  good  substitute 
for  the  common  wire-gauze.  The  Chaddock  burner,  made  of 
non-corrodible  materials,  is  now  obtainable,  and  is  adapted 
to  use  in  the  fume-box.  Electric  heating  apparatus  has  been 
brought  to  considerable  efficiency,  and  will  in  time  supplant 
all  present  methods,  but  the  installation  and  operation  are  as 
yet  costly.  An  incandescent  lamp  may  be  arranged  as  a 
heating  apparatus,  and  is  especially  satisfactory  in  extractions 
and  distillations  with  inflammable  materials.  The  low-tempera- 
ture burner  shown  in  figure  36  is  convenient  in  many  opera- 


APPARATUS    AND    CHEMICALS  63 

tions.  As  sold,  the  inlet  pipe  is  too  short  and  the  rubber 
connection  becomes  hot.  The  inlet  should  be  lengthened  by 
a  piece  of  metal  pipe  (standard  l/%  inch  gas-pipe  is  suitable) 
about  10  cm.  long.  In  default  of  this,  the  joint  may  be  kept 
cool  by  wrapping  around  it  a  piece  of  muslin,  the  ends  of 
which  dip  in  a  vessel  containing  water. 

Filter-papers  are  furnished  in  great  variety,  adapted  to  all 
purposes.  The  so-called  hardened  filters  are  serviceable  in 
several  operations,  such  as  determination  of  crude  fiber,  insolu- 
ble matter,  and  extraction  with  volatile  solvents,  for  with  care 
the  wet  precipitate  can  be  scraped  off  without  removing  an 
appreciable  amount  of  the  filter-paper. 

Glass  rods  slightly  flattened  or  bent 
at  the  middle  to  a  very  obtuse  angle 
are  convenient  because  they  are  not 
liable  to  roll  off  of  beakers  or  funnels. 

Reagents,  especially  those  used  only 
in  small  amounts,  are  most  conveni- 
ently kept  in  capped  bottles,  each  with 
small  glass  tube  or  pipet,  the  tube  be- 
ing just  long  enough  to  reach  above  FIG.  36. 
the  top  of  the  bottle.  In  this  way 

none  of  the  solution  will  get  in  contact  with  the  neck  of  the 
bottle.  Solids  should  be  kept  in  hood-stoppered  bottles,- — 
i.  e.,  those  in  which  the  flat  top  of  the  stopper  is  close  to  the 
bottle,— so  as  to  give  less  chance  for  deposit  of  dust.  All 
chemicals  in  general  use  should  be  kept  in  closed  cases,  ammo- 
nium hydroxid  and  ammonium  carbonate  being  separate  from 
the  common  acids.  The  stock  bottles  for  acids  and  standard 
solutions  should  be  protected  from  dust  by  placing  over  the 
stopper  of  each,  an  inverted  tumbler  large  enough  to  rest  on 
the  top  of  the  body  of  the  bottle. 

Platinum  ware  requires  care  to  prevent  staining  and  crack- 
ing. Substances  containing  any  of  the  easily -reducible  metals 


64  FOOD    ANALYSIS 

must  not  be  heated  in  contact  with  platinum  ;  even  iron  com- 
pounds in  the  presence  of  reducing  agents — e.  g.,  filter-paper — 
will  do  harm.  Sudden  cooling  of  platinum  should  be  avoided, 
as  it  tends  to  make  the  metal  brittle.  After  being  heated  to 
redness  the  metal,  when  cold,  should  be  lightly  rubbed  with 
very  fine  sea-sand  (not  river-sand  nor  powered  quartz  or 
pumice),  by  which  the  metal  will  be  burnished  and  its  texture 
preserved.  The  platinum-pointed  forceps  should  be  treated 
in  the  same  way. 

Platinum  dishes  may  often  be  cleaned  by  rubbing  them 
with  sodium  amalgam,  decomposing  this  by  immersion  in 
water,  and  driving  the  mercury  off  by  heating  to  redness. 
Some  stains  may  be  removed  by  melted  potassium  acid 
sulfate. 

Nickel  dishes  may  be  substituted  for  platinum  in  cases  in 
which  only  gentle  heating  is  required,  but  nickel  is  apt  to  be 
injured  by  direct  heating  with  gas. 

All  the  largely  used  chemicals  are  obtainable  of  good  qual- 
ity, as  a  rule,  but  in  important  investigations  tests  for  purity 
and  strength  should  be  applied.  The  following  notes  will  be 
sufficient. 

Alcohol. — Ethyl  alcohol,  commonly  called  "  grain  alcohol," 
contains  in  its  strongest  commercial  form  about  95  per  cent, 
of  ethyl  hydroxid,  notable  quantities  of  esters,  aldehydes, 
fusel  oil,  and  traces  of  acid.  For  some  purposes — e.  g.,  mak- 
ing standard  solutions  of  alkali — it  must  be  purified  by  redis- 
tillation over  sodium  hydroxid.  The  absolute  alcohol  sold 
by  dealers  usually  contains  some  water.  The  presence  of 
water  in  alcohol  may  be  detected  by  the  evolution  of  acety- 
lene when  a  little  calcium  carbid  is  added.  This  may  also  be 
employed  for  removing  small  amounts  of  water,  the  liquid 
being  then  redistilled,  but  hydrogen  sulfid,  hydrogen  phos- 
phid,  and  ammonium  compounds  may  be  thus  introduced. 
Anhydrous  copper  sulfate  is  turned  blue  by  alcohol  containing 
water. 


APPARATUS  AND  CHEMICALS  65 

Methyl  alcohol.  Crude  wood-alcohol  is  of  limited  use  in 
laboratory  work.  It  contains  much  acetone.  A  purified 
article  is  now  furnished,  under  the  trade  name  "  Columbian 
Spirit,"  which  is  about  98  per  cent,  methyl  hydroxid  and  is 
free  from  notable  amounts  of  impurities.  It  may  be  used 
with  economy  as  a  substitute  for  ethyl  alcohol  in  many  cases. 
It  is  more  volatile,  but  traces  of  strong-smelling  foreign  matters 
may  cause  the  odor  to  persist  longer  than  with  refined  alcohol. 

Ether.  Commercial  ether  contains  notable  amounts  of  al- 
cohol and  water,  but  much  purer  samples  can  be  obtained  from 
dealers  in  laboratory  supplies.  A  method  for  preparing  ether 
for  extraction  purposes  is  given  on  page  50. 

Chloroform,  benzene,  w&  petroleum  spirit  are  usually  obtaina- 
ble of  good  quality,  except  that  all  are  liable  to  contain  water, 
which  is  sometimes  objectionable.  It  may  be  removed  by  use 
of  anhydrous  calcium  sulfate  or  anhydrous  copper  sulfate  and 
redistillation.  Commercial  chloroform  is  liable  to  decomposi- 
tion, t>y  which  it  becomes  acrid.  All  volatile  solvents  are 
liable  to  contain  appreciable  amounts  of  non-volatile  materials. 

Sodium  hydroxid.  Several  brands  sold  for  household  use 
are  suitable  for  ordinary  purposes,  such  as  making  standard 
alkali  or  in  the  Kjeldahl-Gunning  process. 

Potassium  liydroxid.     Purified  grades  should  be  used. 

Sand  and  asbestos  intended  for  moisture  and  extract  deter- 
mination must  be  selected  with  care,  and  dried  thoroughly  be- 
fore weighing.  Common  sand  contains  much  material  other 
than  quartz  ;  asbestos  fiber  is  often  of  inferior  quality. 

Electrolytic  Method  for  Standard  Solutions. — The 
preparation  of  standard  solutions  by  electrolysis  has  been 
investigated  by  R.  K.  Meade,7  who  finds  the  following  method 
accurate  : 

12.487  grams  of  pure  crystallized  copper  sulfate  are  dis- 
solved in  about  750  c.c.  of  hot  water  in  a  1000  c.c.  beaker. 


66  FOOD    ANALYSIS 

When  the  solution  is  cold,  a  cylinder  of  thin  copper  foil  a 
little  more  than  three  times  the  diameter  of  the  beaker  is  rolled 
so  that  the  ends  lap.  The  negative  wire  is  slipped  through 
holes  in  the  lap  and  fastened.  The  beaker  is  covered  by  a  per- 
forated watch-glass,  through  which  a  platinum  wire  for  the 
positive  pole  passes.  A  current  of  1.5  to  2  amperes  is  sent 
through  the  solution  for  at  least  8  hours.  The  terminals  are 
then  well  rinsed,  also  any  copper  that  may  have  dropped,  the 
liquid  decanted  into  the  flask,  made  up  to  mark,  and  mixed. 
The  solution  is  decinormal.  Normal  and  half-normal  can  also 
be  prepared  in  this  manner. 

In  the  preparation  of  standard  solutions  it  must  be  borne 
in  mind  that  graduated  apparatus  is  not  only  often  inaccurate, 
but  the  systems  of  standardizing  it  are  not  wholly  uniform. 
It  is  to  be  regretted  that  some  of  the  dealers  in  reagents  have 
not  established  a  system  of  supplying  standard  solutions  of 
certain  reagents  of  absolutely  uniform  strength. 

Indicators. — For  ordinary  laboratory  work  litmus,  phenol- 
phthalein,  and  methyl-orange  are  usually  preferred. 

Litmus.  Litmus  solution  is  now  little  used.  It  is  prepared 
by  treating  the  commercial  material  with  water  and  filtering 
the  solution  after  sufficient  color  has  dissolved.  It  must  be 
kept  in  an  open  bottle.  Intermediate  litmus-paper,  which  is 
convenient  for  ascertaining  the  reaction  of  liquids,  is  prepared 
as  follows  :  A  clear,  fresh  solution  of  litmus  is  divided  into 
two  equal  portions  ;  one  of  these  is  rendered  purple-red  (not 
bright  red)  by  the  cautious  addition  of  dilute  nitric  acid  ;  the 
other  portion  is  then  added  and  strips  of  good  filter-paper 
soaked  in  the  liquid  and  dried  quickly.  This  paper  will  be 
affected  by  ordinary  acid  or  alkaline  solutions.  It  should 
be  kept  in  the  dark,  protected  from  dust. 

Plienolplithalein.  A  solution  of  I  gram  in  100  c.c.  of  good 
(methyl  or  ethyl)  alcohol  is  sufficient  and  keeps  well. 


APPARATUS    AND    CHEMICALS  6/ 

Methyl-orange.  A  solution  of  o.  I  gram  in  water  will  be 
satisfactory.  In  titrating  with  methyl-orange  very  little  of 
the  indicator  should  be  used. 

Cochineal.  Many  prefer  this  indicator  for  titrating  ara- 
moniun  hydroxid.  The  following  description  is  given  by  the 
A.  O.  A.  C.  in  connection  with  the  Kjeldahl-Gunning  process  : 
3  grams  of  powdered  cochineal  are  macerated  for  several 
days,  with  occasional  shaking,  in  alcohol  of  about  20  per 
cent.,  and  the  solution  filtered. 


APPLIED   ANALYSIS 

GENERAL   METHODS 

POISONOUS    METALS 

The  elements  included  under  this  title  are  mercury,  arsenic, 
lead,  tin,  copper,  and  zinc.  Some  very  poisonous  elements 
are  not  likely  to  be  encountered  in  foods,  and  therefore  are 
not  considered  in  this  connection. 

A.  H.  Allen  8  has  devised  a  general  process  for  the  de- 
tection of  poisonous  metals.  A  convenient  quantity  of  the 
substance,  say  25  grams,  is  mixed  in  a  porcelain  crucible  by 
degrees  with  sufficient  strong  sulfuric  acid  to  moisten  the 
mass  thoroughly  without  making  it  fluid.  About  2  c.c.  will 
generally  be  required.  Liquid  material  should  be  evapo- 
rated to  dryness  or  nearly  so  at  a  low  temperature  before  being 
treated  with  the  acid.  The  crucible  is  heated  for  a  short  time 
on  the  water-bath,  after  which  the  temperature  is  gradually 
raised  to  a  point  below  that  required  to  volatilize  the  sulfuric 
acid,  and  maintained  until  the  action  seems  to  be  complete. 
It  is  not  necessary  to  carry  on  this  part  of  the  process  until 
the  carbon  is  burnt  off.  The  crucible  is  allowed  to  cool, 
about  I  c.c.  of  strong  nitric  acid  added,  and  the  heating  con- 
tinued until  red  fumes  are  evolved.  Recently  ignited  mag- 
nesia, in  the  proportion  of  0.5  gram  for  each  cubic  centi- 
meter of  the  acid  used,  is  incorporated  with  the  mass  and  the 
mixture  burned  off  at  a  dull  red  heat,  preferably  in  a  muffle. 
After  cooling,  the  ash  is  moistened  with  nitric  acid,  again 
burned  off,  and  the  process  repeated  until  all  the  carbon  is 
consumed.  The  residue  is  treated  with  0.5  c.c.  of  sulfuric 

68 


POISONOUS    METALS 


69 


acid,  heated  until  fumes  are  evolved,  cooled,  boiled  with  water, 
diluted  without  filtration  to  about  100  c.c.,  saturated  with 
hydrogen  sulfid,  the  solution  filtered  and  examined  according 
to  the  following  scheme  : 


AQUEOUS  SOLUTION  may  contain  zinc,  iron 
and  earthy  phosphates.  Add  bromin 
water  to  destroy  hydrogen  sulfid,  coti- 

'  vert  iron  into  the  ferric  state,  boil,  then 
add  excess  of  ammonium  hydroxid,  boil 
again,  and  filter. 


PRECIPITATE  AND  RESIDUE  may  contain 
lead  sulfid,  stannic  oxid,  copper  sulfid,  or 
calcium  sulfate.  Fuse  in  porcelain  cru- 
cible for  10  minutes  with  2 grams  of  mixed 
potassium  and  sodium  carbonate's  and  i 
gram  of  sulfur.  When  cool,  boil  with 
water  and  filter. 


PRECIPI- 

FILTRATE   if    blue,    contains 

RESIDUE.    Boil  with  strong  hy- 

FILTRATE. 

TATE 
may  con- 
tain iron 

nickel.     Divide  into  two  por- 
tions : 

drochloric  acid  as  long  as  hy- 
drogen sulfid  is  evolved,  add 
a  few  drops  of  bromin  water 

Acidu- 
late with 
acetic 

and  phos- 

to complete  the  oxidation  of 

acid.      A 

phates. 

the  copper  sulfid,  and  filter 

yellow 

if  necessary.    To  the  filtrate 

precipi- 

add excess  of  ammonium  hy- 

tate    of 

droxid,  when   a  blue  color- 

stannic 

ation  will    be  indicative  of 

sulfid  in- 

copper.    Acidulate  the  liquid 

d  i  cates 

with  acetic  acid  and  divide 

tin. 

into  two  portions  : 

I.  Heat  to  boil- 
ing and  add 

II.    If    zinc 
found    in    I, 

I.  Add    potas- 
sium    chro- 

II.  Add  potas- 
sium    ferro- 

i 

pot  assiu  m 

for  its  deter- 

mate.      A 

cyanid.     A 

ferrocyanid. 
White     pre- 

m i  na  t  i  on, 
acidulate 

yellow    pre- 
cipitate    in- 

brownish 
precipitate 

cipitate      or 

the  ammoni- 

dicates  lead. 

or      colora- 

turbidity in- 

acal solution 

tion        indi- 

dicates zinc. 

strongly 

cates  copper. 

with    acetic 

acid,  filter,  if 

n  ecessary, 

and  precipi- 

tate the  zinc 

from  the  fil- 

trate by  hy- 

drogen   sul- 

fid.     Any 

nickel  pres- 

ent will  also 

be     precipi- 

tated. 

Allen's  scheme  does  not  include  chromium,  which  may  be 
present  as  a  constituent  of  lead  chromate  and  will  be  found 
almost  entirely  in  the  precipitate  and  residue  insoluble  in 
water.  For  its  detection  a  portion  of  this  or  of  the  original 
ash  may  be  fused  with  sodium  carbonate  and  potassium 
chlorate,  the  yellow  melt  containing  chromate  dissolved  in 


70  FOOD    ANALYSIS 

the  smallest  possible  quantity  of  water  and  slightly  acidulated 
with  hydrochloric  acid.  The  liquid  is  then  added  to  a  test- 
tube  containing  a  small  amount  of  hydrogen  dioxid  overlaid 
with  a  little  ether.  In  the  presence  of  a  chromate  the  water 
will  acquire  a  blue  color,  which  on  slight  shaking  will  pass 
into  the  ethereal  layer. 

When  tin  is  known  to  be  present,  the  amount  may  be  found  , 
by  treating  the  precipitate  of  stannic  sulfid  with  strong  nitric 
acid,  igniting  the  metastannic  acid  formed,  and  weighing  the 
resultant  stannic  acid.  For  the  detection  of  tin  it  is  recom- 
mended to  treat  the  stannic  sulfid  with  hydrochloric  acid  and 
bromin  water  and  boil  the  filtered  liquid  with  iron  wire  to 
reduce  to  the  stannous  condition.  The  liquid  is  diluted  and 
decanted  from  the  undissolved  iron  and  any  precipitated 
material,  and  the  tin  detected  by  adding  a  drop  of  mercuric 
chlorid  solution,  which  will  produce  a  white  or  gray  turbidity 
according  to  the  amount  of  tin  present. 

Copper  may  be  estimated  colorimetrically  by  means  of 
ammonium  hydroxid  or  potassium  ferrocyanid.  According 
to  Bodmer  and  Moor,  for  very  small  amounts  the  ferrocyanid 
method  is  the  most  accurate.  Paul  and  Cownley  estimate 
copper  as  follows  :  The  sample  is  carbonized  in  a  platinum 
dish  and  extracted  with  a  little  hydrochloric  acid  ;  the  insolu- 
ble residue  is  ignited  with  a  little  nitric  acid,  hydrochloric 
acid  added,  and  the  resulting  mixture  added  to  the  original 
extract.  The  solution  is  then  concentrated  to  about  30  or  40 
c.c.,  placed  in  a  weighed  platinum  dish,  and  the  copper  depos- 
ited with  pure  zinc.  If  the  deposit  is  not  of  true  copper 
color,  it  is  dissolved  in  a  little  nitric  acid  and  the  copper 
determined  colorimetrically. 

Zinc. — Wiley  determines  the  amount  of  zinc  in  evaporated 
fruits  as  follows  :  The  sample  is  placed  in  a  large  platinum 
dish  and  heated  slowly  until  dry  and  in  incipient  combustion. 
The  flame  is  removed  and  the  combustion  allowed  to  proceed, 


POISONOUS    METALS  /I 

the  lamp  being  applied  from  time  to  time,  in  case  the  burning 
ceases.  The  mass,  when  burned  out,  consists  of  ash  and  char. 
It  is  ground  to  fine  powder  and  extracted  with  hydrochloric 
or  nitric  acid,  the  residual  char  is  burned  to  whiteness  at  a  low 
temperature,  the  ash  extracted  with  acid,  the  soluble  portion 
added  to  the  first  extract,  and  the  whole  filtered.  A  drop  of 
methyl-orange  solution  is  placed  in  the  liquid  and  ammonium 
hydroxid  added  until  it  is  only  faintly  acid.  The  iron  is  pre- 
cipitated by  adding  50  c.c.  of  a  solution  of  ammonium  acetate, 
250  grams  to  the  liter,  and  raising  the  temperature  to  about 
80°.  The  precipitate  is  separated  by  filtration,  washed  in 
water  at  80°  until  free  from  chlorid,  the  filtrate  saturated 
with  hydrogen  sulfid,  allowed  to  stand  until  the  zinc  sulfid 
settles,  and  poured  on  a  close  filter.  It  is  often  necessary  to 
return  the  filtrate  several  times  before  it  becomes  limpid.  The 
collected  precipitate  is  washed  with  a  saturated  solution  of 
hydrogen  sulfid  containing  a  little  acetic  acid.  The  precipi- 
tate and  filter  are  transferred  to  a  crucible,  dried,  ignited,  and 
the  oxid  weighed. 

Arsenic,  if  present  in  amount  sufficient  to  be  of  sanitary 
significance,  may  be  detected  by  Reinsch's  test,  a  liberal 
amount  of  hydrochloric  acid  being  used,  since  arsenates  do 
not  otherwise  respond  to  the  test.  Some  water  strongly  acid- 
ulated with  hydrochloric  acid  is  placed  in  a  test-tube,  about 
half  a  square  centimeter  of  bright  copper  foil  added,  and  the 
liquid  boiled  gently  for  a  few  minutes.  If  the  copper  remains 
bright,  showing  that  the  reagents  contain  no  arsenic,  the 
material  to  be  tested  is  added  and  the  liquid  again  boiled  for 
several  minutes.  If  arsenic  be  present,  a  steel-gray  stain  will 
appear  on  the  copper.  The  slip  is  removed,  washed  with  dis- 
tilled water,  dried  by  pressure  between  filter-paper,  placed  at 
the  closed  end  of  a  narrow  glass  which  has  been  previously 
dried  by  heating  nearly  to  redness.  The  tube  is  gently  heated 
at  the  point  at  which  the  copper  rests.  The  arsenic  will  be 


72  FOOD    ANALYSIS 

converted  into  arsenous  oxid,  which  will  collect  on  the  cooler 
portions  of  the  tube  in  octahedral  crystals. 

Reinsch's  test  cannot  be  applied  in  the  presence  of  active 
oxidizing  agents,  such  as  chromates,  chlorates,  or  nitrates. 

Gutzeit's  test,  which  is  more  delicate,  is  as  follows  :  Place 
in  a  tall  test-tube  about  a  gram  of  pure  zinc,  5  c.c.  of  diluted 
sulfuric  acid  (6  per  cent.),  and  I  c.c.  of  the  sample.  The 
mouth  of  the  test-tube  is  covered  with  a  tightly-fitting  cap  of 
three  thicknesses  of  filter-paper.  A  drop  of  strong  solution 
of  silver  nitrate  is  placed  on  the  upper  paper  and  the  tube 
allowed  to  stand  for  10  minutes  in  the  dark.  If  arsenic  be 
present,  a  bright  yellow  stain  will  appear  on  the  filter-paper, 
which,  on  the  addition  of  water,  becomes  black  or  brown.  A 
blank  test  should  always  be  made  to  establish  the  purity  of 
the  reagents.  Sulfids  (which  may  be  detected  by  substituting 
lead  acetate  for  the  silver  nitrate  in  the  above  test)  must  be 
oxidized  to  sulfates  before  applying  the  test. 

The  test  is  delicate.  A  less  rigorous  one  may  be  made  by 
substituting  a  drop  of  a  saturated  solution  of  mercuric  chlorid 
for  the  silver  nitrate.  If  no  yellow  coloration  appears  after  10 
minutes,  the  sample  may  be  considered  free  from  arsenic. 

The  purity  of  the  reagents  must  be  carefully  ascertained 
before  applying  any  of  these  methods. 


COLORS 

At  present,  the  colors  used  in  food-articles  are  mostly 
synthetic  products,  commonly  called  "  anilins,"  but  largely 
derived  from  other  coal-tar  materials. 

Natural  organic  colors — annatto,  cochineal,  turmeric,  indigo, 
saffron,  and  chlorophyl — are  used  to  a  limited  extent,  but  the 
mineral  colors,  such  as  lead  chromate  and  ferric  oxid,  are 
rarely  employed. 

The   National  Association   of  Confectioners  of  the  United 


COLORS  73 

States  has  published  a  list  of  forbidden  and  permitted  colors, 
and  many  manufacturers  are  following  the  suggestions  therein 
made.  A  summary  of  this  list  is  herewith  presented.  The 
nomenclature  of  the  colors  is  much  confused,  but  the  list  has 
a  suggestive  value. 

FORBIDDEN 

All  colors  containing  appreciable  amounts  of  mercury,  lead, 
copper,  arsenic,  antimony,  tin,  zinc,  chromium,  cadmium,  and 
barium. 

PONCEAU  3RB — Ponceau  B  extra,  Fast  Ponceau  B,  New 
Red  L,  Scarlet  EC,  Imperial  Scarlet,  Old  Scarlet,  Biebrich 
Scarlet. 

CROCEIN  SCARLET  36 — Ponceau  4RB. 

COCHENILLE  RED  A — Crocein  Scarlet  46  and  G,  Brilliant 
Scarlet,  Brilliant  Ponceau  4R,  Ponceau  4R,  Ponceau 
Brilliant  4R,  New  Coccin  Scarlet. 

CROCEIN  SCARLET  76 — Crocein  Scarlet  8B,  Ponceau  6RB. 

CROCEIN  SCARLET  O  Extra. 

SAFRANIN — Safranin  T,  Safranin  extra  G,  Safranin  G  extra, 
GGSS,  Safranin  GOOO,  Safranin  FF  extra,  No.  O,  Safranin 
cone,  Safranin  AG  extra,  Safranin  AGT  extra,  Anilin  pink. 

GUM  GUTTA. 

PICRIC  ACID. 

MARTIUS  YELLOW — Naphthylamin  yellow,  Jaune  d'or,  Man- 
chester yellow,  Naphthalene  yellow,  Naphthol  yellow. 

ACME  YELLOW — Chrysoin,  Chryseolin  yellow  T,  Gold  yellow, 
Resorcin  yellow,  Acid  yellow  RS,  Tropeolin  O,  Jaune  II. 

VICTORIA  YELLOW — Victoria  Orange,  Anilin  Orange,  Dinitro- 
cresol,  Saffron  Substitute,  Golden  yellow. 

ORANGE  II — Orange  II,  Orange  P,  Orange  extra,  Orange  A, 
Orange  G,  Acid  Orange,  Gold  Orange,  Mandarin  G  extra, 
7 


74  FOOD    ANALYSIS 

/9-Naphthol  orange,  Tropeolin  OOO  2,  Mandarin,  Chry- 
saurin. 

METANIL  YELLOW — Orange  MN,  Tropeolin  G,  Victoria  yel- 
low (O  double  cone.),  Jaime  G,  Metanil  extra. 

SUDAN  I — Carminnaphthe. 

ORANGE  IV — Orange  IV,  Orange  N,  Orange  GS ;  New  yel- 
low, Acid  yellow  D,  Tropeolin  OO,  Fast  yellow,  Diphen- 
ylorange,  Diphenylamin  Orange,  Anilin  yellow. 

NAPHTHOL  GREEN  B. 

METHYLENE  BLUE  BBG — Methylene  Blue  BB,  in  powder 
extra,  Methylene  Blue  DBB,  extra,  Methylene  Blue  BB, 
(Crystalline),  Ethylene  Blue,  Methylene  Blue  BB. 

BISMARCK  BROWN — Bismarck  brown  G,  Manchester  brown, 
Phenylene  brown,  Vesuvin,  Anilin  brown,  Leather  brown, 
Cinnamon  brown,  Canelle,  English  brown,  Gold  brown. 

VESUVIN  B — Manchester  brown  EE,  Manchester  brown  PS, 
Bismarck  brown,  Bismarck  brown  T. 

FAST  BROWN  G — Acid  brown. 

CHRYSOIDIN — Chrysoidin  G,  Chrysoidin  R,  Chrysoidin  J, 
Chrysoidin  Y. 

PERMITTED 

ULTRAMARINE  BLUE. 

ULTRAMARINE  VIOLET. 

MANGANESE  BROWN. 

CHOCOLATE  BROWN  and  colors  of  a  similar  nature  have  as 
their  basis  natural  or  precipitated  ferric  oxid  which  in  an 
impure  condition  may  have  small  quantities  of  arsenic  in 
its  composition.  It  is  possible  with  proper  care  to  secure 
raw  material  entirely  free  from  this  objectionable  element 
and  no  ferric  oxid  containing  any  traces  of  arsenic  should 
be  used  in  the  preparation  of  color. 

ULTRAMARINE  GREEN. 


COLORS  7  5 

COCHINEAL  CARMIN. 

CARTHAMIC  ACID  (from  saffron). 

RED  WOOD. 

ARTIFICIAL  ALIZARIN  AND  PURPURIN. 

CHERRY  AND  BEET  JUICES. 

EOSIN — Eosin  A,  Eosin  G  extra,  Eosin  GGF,  Eosin  JJJ, 
Eosin  JJJJ  extra,  Eosin  extra,  Eosin  KS,  Eosin  DH,  Eosin 
JJF. 

ERYTHROSIN — Erythrosin  D,  Erythrosin  B,  Pyrosin  B,  Prim- 
rose Soluble,  Eosin  J,  Dianthin  B. 

ROSE  BENGALE — Rose  Bengale  N,  Rose  Bengale  AT,  Rose 
Bengale  G. 

PHLOXIN — Phloxin  TA,  Eosin  blue,  Cyanosin,  Eosin  10  B. 

BORDEAUX  AND   PONCEAU  reds  resulting  from  the  action   of 
Naphtholsulfonic  acids  on  diazoxylenes. 
PONCEAU    2   R — Ponceau    G,    Ponceau    GR,    Ponceau    R, 
<  Brilliant  Ponceau  G,  Ponceau  J. 
BORDEAUX  B — Fast  Red  B,  Bordeaux  BL,   Bordeaux  G, 

Bordeaux  R  extra,  Cerasin,  Rouge  B. 
PONCEAU  GG — Brilliant  Ponceau  GG,  Ponceau  JJ. 

FUCHSIN  S — Acid  Magenta,  Rubin  S,  and  Fuchsin. 

ARCHIL  SUBSTITUTE — Naphthion  red. 

ORANGE  I — Orange  No.  I,  Naphthol  orange,  a- Naphthol 
orange,  Tropeolin  OOO  I. 

CONGO  RED. 

AZORUBIN    S — Azorubin,    Azorubin    A,    Azoacidrubin,    Fast 
red  C,  Carmoisin,  Brilliant  Carmoisin  O. 

FAST  RED  D — Fast  red  EB,  Fast  red  NS,  Amaranth,  Azo- 
acidrubin BB,  Bordeaux  DH,  Bordeaux  S,  Naphthol  red  S, 
Naphthol  red  O,  Victoria  ruby,  Wool  red  (extra). 

FAST  RED — Fast  red  E,  Fast  red  S,  Acid  Carmoisin  S. 


7  6  FOOD    ANALYSIS 

PONCEAU  4  GB — Crocein  Orange,  Brilliant  Orange  G,  Orange 

GRX,  Pyrotin  Orange,  Orange  ENL. 
METANITRAZOTIN. 
ANNATTO. 
SAFFRON. 
SAFFLOWER. 
TURMERIC. 
NAPHTHOL  YELLOW  S — Citronin  A,  Sulphur  yellow  S,  Anilin 

yellow   S,  Anilin  yellow,  Succinin,    Saffron  yellow,  Solid       / 

yellow,  Acid  yellow  S. 
BRILLIANT  YELLOW  (Schoelkopf ). 
PONCEAU  4  GB — Crocein  Orange,  Brilliant  Orange  G,  Orange 

GRX,  Pyrotin  Orange,  Orange  ENL. 
FAST  YELLOW — Fast  yellow  G,  Fast  yellow  (greenish),  Fast 

yellow  S,  Acid  yellow,  New  yellow  L. 
FAST  YELLOW  R. 
AZARIN  S. 
ORANGE  —  Orange    GT,    Orange    RN,    Brilliant    Orange    O, 

Orange  N. 
SPINACH  GREEN. 
CHINESE  GREEN. 
MALACHITE  GREEN — Malachite  green  B,  Benzaldehyde  green, 

New  Victoria  green,  New  green,  Solid  green  crystals,  Solid 

green  O,  Diamond  green,   Diamond  green  B,  Fast  green, 

Bitter  Almond-oil  green. 
DINITROSORESORCIN — Solid   green    O,  in   paste,   Dark  green, 

Chlorin,  Russia  green,  Alsace  green,  Fast  green,  Resorcinol 

green. 
INDIGO. 
LITMUS. 
ARCHIL  BLUE. 


COLORS  77 

GENTIAN  BLUE  6  B — Spirit  Blue,  Spirit  Blue  PCS,  Opal  Blue, 

Hessian  Blue,  Light  Blue. 
COUPIER'S  Blue — Fast  blue  R  and  B,  Solid  blue  RR  and  B, 

Indigin  DF,  Indulin  soluble  in  alcohol,  Indophenin  extra, 

Blue  CB  (soluble  in  alcohol),  Nigrosin  (soluble  in  alcohol). 

IN  GENERAL  such  blue  colors  as  are  derived  from  Triphenyl- 
rosanilin  or  from  Diphenylamin. 
PARIS  VIOLET — Methyl  violet  B  &  BB,  Methyl  violet  V  3, 

Pyoktanin,  Malbery  blue. 
WOOL  BLACK. 
NAPHTHOL  BLACK  P. 
AZOBLUE. 
MAUVEIN — Rosolan,  Violet  paste,  Chrome  violet,  Anilin  violet, 

Anilin  purple,  Perkins  violet,  Indisin,  Phenamin,  Purpurin, 

Tyralin,  Tyrian  purple,  Lydin. 
CARAMEL. 
LICORICE. 
CHRYSAMIN  R. 

The  identification  of  individual  colors  in  mixture  with  foods 
or  beverages  is  usually  difficult,  often  impossible,  with  methods 
at  present  available.  It  is  possible  in  many  cases  to  distin- 
guish between  artificial  and  natural  colors  ;  for  example,  to 
determine  whether  a  sample  of  wine  owes  its  color  to  a  coal- 
tar  derivative  or  to  the  coloring-matter  of  the  grape.  Special 
methods  for  determining  such  points  will  be  given  in  connec- 
tion with  examination  of  articles  that  are  liable  to  be  artifi- 
cially colored.  The  following  general  test,  known  as  Arata's 
wool-test,  is  very  serviceable.  White  wool  or  woolen  cloth 
is  cleaned  by  boiling  for  a  few  minutes,  in  water  containing 
0.5  per  cent,  of  sodium  hydroxid  and  washed  with  clean 
water  until  all  alkali  is  removed.  A  convenient  quantity  of 
the  substance  to  be  tested  (e.  g.,  about  100  grams  ot  wine  or 


/8  FOOD    ANALYSIS 

fruit  juice)  is  mixed  with  one  per  cent,  of  potassium  acid  sul- 
fate,  heated  to  boiling,  the  washed  wool  manipulated  in  the 
liquid  for  a  few  minutes,  washed  well  in  boiling  water,  and 
dried.  The  natural  coloring-matters  of  wines  and  fruits  leave 
the  wool  uncolored  or  give  merely  a  pink  or  brown  tint, 
which  is  changed  to  green  by  ammonium  hydroxid  and  not 
restored  by  washing  with  water ;  but  with  many  artificial 
colors  the  wool  is  dyed  to  a  color  which  is  either  not  changed 
by  ammonium  hydroxid  or,  if  changed,  is  restored  by  wash- 
ing in  water. 

When  dyes  intended  for  food-coloring  are  to  be  examined 
in  bulk,  the  following  methods  are  advantageous  : 

A  small  quantity  of  the  sample  (o.  I  to  0.25  gram)  is  heated 
on  platinum  foil.  Nitro-colors  show  more  or  less  deflagra- 
tion at  first.  Sulfonated  colors  form  a  fusible  residue,  in 
which  the  carbon  burns  with  difficulty.  It  will  be  advanta- 
geous to  add  some  oxidizing  agent  (potassium  nitrate,  potas- 
sium chlorate,  or  sodium  nitrate).  It  is  not  necessary  to 
burn  off  all  the  carbon.  The  mass  is  allowed  to  cool,  boiled 
up  with  water  acidulated  with  hydrochloric  acid  (this  may 
cause  the  evolution  of  a  little  hydrogen  sulfid),  and  barium 
chlorid  added.  A  copious  white  precipitate  will  occur  if  the 
color  is  a  sulfonated  one. 

For  detection  of  arsenic  the  Reinsch  test  may  be  applied  or 
the  color  may  be  examined  for  all  the  important  poisonous 
metals  by  the  scheme  given  on  page  69. 

Identification  of  colors  may  sometimes  be  accomplished  by 
the  scheme  on  pages  80,  81,  and  82,  which  is  A.  G.  Green's 
adaptation  of  Weingartner's  tables.  It  is  reproduced  without 
modification  of  spelling  or  nomenclature  from  A.  H.  Allen's 
" Commercial  Organic  Analysis,"  edited  by  J.  M.  Matthews.9 
The  reagents  required  are  as  follows  : 

Tannin  solution :  Tannin,  I  gram  ;  sodium  acetate,  I  gram  ; 
water,  10  c.c. 


COLORS  79 

Zinc  dust. 

Dilute  hydroMoric  acid :  Hydrochloric  acid,  5  c.c.  ;  water, 
15  c.c. 

Ammonium  hydroxid  solution. 

Chromic  acid  solution  :  Chromic  acid,  I  gram  ;  water,  looc.c. 

Chromic-sulfuric  acid  solution :  Chromic  acid,  I  gram  ; 
strong  sulfuric  acid,  2.5  c.c.  ;  water,  100  c.c. 

Strong  sodium  hydroxid  solution:  Sodium  hydroxid,  33 
grams  ;  water,  67  c.c. 

Dilute  sodium  hydroxid  solution:  Sodium  hydroxid,  5 
grams  ;  water,  95  c.c. 

Alcohol.     70  per  cent. 

In  applying  the  scheme  a  primary  division  is  made  into 
dyes  soluble  and  insoluble  in  water.  The  former  are  divided 
by  means  of  the  tannin  solution  into  the  so-called  basic  and 
acid  groups.  The  dyes  which  in  aqueous  solution  are  precipi- 
tated by  tannin  solution  are  termed  basic  dyes. 

The  reduction  with  zinc  dust  is  best  made  by  adding  a  little 
of  the  zinc  dust  to  the  hot  dyestuff  solution  contained  in  a 
test-tube,  agitating,  and  adding  dilute  hydrochloric  acid  drop 
by  drop  until  decolorized.  Excess  of  acid  should  be  care- 
fully avoided.  When  the  color  acid  is  quite  insoluble,  the 
reduction  is  made  with  zinc  dust  and  ammonium  hydroxid. 
The  reduced  solution  is  decanted  upon  a  small  filter ;  if  the 
color  does  not  return  in  a  few  minutes,  the  paper  is  moistened 
with  chromic  add  solution.  In  the  case  of  acid  colors  the 
chromic-sulfuric  acid  solution  should.be  used.  As  some  dyes 
do  not  show  their  color  in  presence  of  free  acids,  the  paper 
should  be  exposed  to  the  fumes  of  strong  ammonium  hy- 
droxid solution  before  deciding  as  to  whether  the  color  will 
return. 

Tests  adapted  to  the  recognition  of  colors  in  particular 
foods  will  be  described  in  connection  with  such  foods. 


80 


FOOD    ANALYSIS 


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PRESERVATIVES  8  3 

PRESERVATIVES 

The  decomposition  of  food  is  prevented  by  sterilization  or 
by  addition  of  antiseptics.  Numerous  food-preservatives  are 
now  in  use.  Some — e.  g.,  common  salt,  niter,  acetic  acid,  and 
wood  smoke — have  been  known  from  early  times  and  are  still 
in  vogue.  Among  the  more  important  of  the  newer  forms  are 
salicylic  acid,  benzoic  acid,  sodium  benzoate,  beta-naphthol, 
saccharin,  abrastol,  formaldehyde,  fluorids,  silicofluorids,  sul- 
fites,  boric  acid,  and  borax.  Other  forms,  principally  synthetic 
coal-tar  derivatives,  have  been  suggested  and,  to  a  limited 
extent,  used.  Most  acids  are  antiseptic. 

Each  of  the  substances  above  enumerated  has  special  adap- 
tabilities ;  some  of  them  are  widely  applicable,  and  hence  are 
largely  used.  Most  of  the  permissible  food-preservatives  are 
not  distinctly  germicidal  and  must  remain  in  the  food  if  con- 
tinued preservation  is  desired. 

Salicylic  acid  may  be  obtained  from  natural  sources,  but  the 
artificial  product  made  from  phenol  is  almost  always  used.  It 
is  apt  to  contain  injurious  by-products.  The  commercial 
article  is  a  white  crystalline  powder,  soluble  in  about  500  parts 
by  weight  of  cold  water,  and  more  freely  soluble  in  a  solution 
of  borax  and  in  alcohol,  ether,  or  petroleum  spirit.  The  last 
two  liquids  extract  it  from  an  acidified  watery  solution.  It 
distils  in  a  current  of  steam.  Its  most  characteristic  reaction 
is  the  violet  color  produced  with  ferric  chlorid. 

Sodium  benzoate,  now  largely  prepared  from  the  artificial 
acid,  derived  from  toluene,  is  usually  sold  as  a  granular  white 
powder  which  has  a  slight  aromatic  odor  and  a  nauseous  taste. 
The  latter  is  of  some  advantage,  since  it  prevents  too  liberal 
use  in  food  articles.  It  is  freely  soluble  in  water  and  has 
marked  antiseptic  qualities.  In  the  United  States,  sodium 
benzoate  is  the  most  common  preservative  for  catsups,  jams, 
jellies,  mince-meat,  and  preserves. 


84  FOOD    ANALYSIS 

Benzole  acid  is  not  frequently  used  in  food  articles,  but  some 
of  it  may  be  formed  from  sodium  benzoate  by  the  action  of  acids 
or  acid  salts  in  the  food.  It  is  necessary,  however,  to  insure 
the  liberation  of  the  benzoic  acid  when  testing  for  it  by  the 
addition  of  sulfuric  acid. 

Saccharin.  Commercial  saccharin  is  somewhat  variable  in 
composition.  It  is  a  white,  crystalline,  intensely  sweet 
powder,  soluble  in  1000  parts  of  cold  and  100  parts  of  boil- 
ing water.  It  is  more  soluble  in  alcohol,  glycerol,  and  ether, 
and  very  slightly  soluble  in  chloroform,  benzene,  and  petro- 
leum spirit.  Ether  removes  it  from  its  aqueous  solutions. 
Pure  saccharin  is  slightly  volatile  at  100°  and  leaves  no  ash, 
but  impurities  may  be  present  in  the  form  of  sodium  salts, 
and  considerable  ash,  principally  sodium  sulfate,  may  be  left 
upon  ignition. 

$-naphthol  is  a  white  crystalline  powder,  slightly  soluble  in 
water,  freely  in  alcohol,  ether,  chloroform,  benzene,  fats,  and 
alkaline  solutions.  It  is  wholly  volatile  on  ignition.  It  is 
liable  to  contain  small  amounts  of  the  more  toxic  isomeric 
form,  a-naphthol.  The  so-called  hydronaphthol  is  substanti- 
ally the  same  as  /9-naphthol. 

Abrastol  or  asaprol  (calcium  /3-naphthol-a-monosulfonate) 
is  a  colorless  or  light  reddish  powder  freely  soluble  in  water 
or  alcohol. 

Formaldehyde  is  a  gas  freely  soluble  in  water,  from  which 
solution  a  polymeric  modification  is  easily  obtained  as  a  white 
solid,  volatilized  only  at  a  temperature  above  the  boiling- 
point  of  water.  Formaldehyde  is  principally  sold  as  a  40  per 
cent,  watery  solution  designated  by  the  copyrighted  name 
"  formalin."  More  dilute  solutions  are  .sold  under  a  variety 
of  fanciful  and  misleading  names.  The  40  per  cent,  solution 
is  a  colorless  liquid  with  a  slight  and  not  disagreeable  odor 
and  a  faint  acid  reaction,  the  last  property  being  probably  due 
to  small  amounts  of  formic  or  acetic  acid  produced  by  oxida- 


PRESERVATIVES  8  5 

* 

tion.  When  this  solution  is  boiled,  the  formaldehyde  distils 
readily  with  the  steam  ;  but  if  the  fresh  distillate  be  evapo- 
rated at  a  lower  temperature, — as,  for  example,  on  a  shallow 
dish  placed  over  boiling  water, — a  large  part  is  converted  into 
the  solid  form.  All  the  modifications  of  formaldehyde  have 
active  reducing  qualities  and  exhibit  strong  tendency  to  com- 
bine with  proteids  so  as  to  form  insoluble  bodies.  A  small 
percentage  of  formaldehyde,  for  example,  will  cause  a  gelatin 
solution  to  solidify  so  that  the  mass  cannot  be  melted  at  any 
temperature  below  that  of  destructive  decomposition.  In  the 
preservation  of  food  the  commercial  formalin  is  almost  ex- 
clusively used. 

Sulfites.  The  acid  salts  are  more  active  than  the  neutral 
form  and  are  more  used.  Calcium  sulfite  is  also  frequently 
employed.  Sulfites  are  white  solids  freely  soluble  in  water 
and  glycerol,  but  not  appreciably  in  alcohol,  or  the  solvents 
immiscible  with  water.  Their  antiseptic  action  being  strongly 
exerted  upon  yeast,  they  have  been  used  largely  to  control  or 
prevent  alcoholic  fermentation.  The  detection  of  sulfites 
being  based  upon  the  recognition  of  the  sulfurous  acid  derived 
from  them,  a  specific  description  of  each  will  not  be  needed. 

Boric  acid  and  borax.  The  observations  of  R.  T.  Thomson 
have  shown  that,  at  least  with  milk,  a  mixture  of  these  sub- 
stances is  more  efficient  than  either  alone,  and  the  two  are 
very  frequently  sold  in  mixture  under  trade  names,  such  as 
"  Preservaline  "  and  "  Rex  Magnus."  They  are  also  used 
separately,  boric  acid  being  the  more  common.  Both  are 
white  powders  soluble  in  water  ;  borax  is  practically  insolu- 
ble in  alcohol,  boric  acid  freely  soluble.  Both  are  non-volatile 
at  a  red  heat,  but  a  watery  solution  of  boric  acid  cannot  be 
evaporated  without  considerable  of  the  acid  passing  off  with 
the  steam.  Borax  has  an  alkaline  reaction  ;  boric  acid  is 
acid  to  litmus,  but  turns  turmeric  paper  brown  when  its  solu- 
tion is  evaporated  on  it.  From  a  solution  of  boric  acid  in 


86  FOOD    ANALYSIS 

methyl  alcohol  the  whole  of  the  acid  may  be  obtained  by 
distillation,  which  is  utilized  in  the  determination. 

When  boric  acid  is  heated  with  glycerol,  tritenyl  borate  is 
produced  as  a  thick  sirup  miscible  in  all  proportions  with  cold 
water  and  decomposed  by  hot  water.  By  evaporation  it  can 
be  obtained  in  the  form  of  a  transparent,  glassy,  brittle  mass 
which  absorbs  water  readily.  A  preparation  made  by  dis- 
solving borax  in  glycerol  has  also  been  offered  as  a  preserva- 
tive, but  is  little  used.  These  glycerol  preparations  have  been 
sold  under  various  names,  such  as  "  boroglyceride "  and 
"glyceride  of  boric  acid." 

Fluorids,  borofluorids,  and  silicofluorids.  Of  these,  the  sodium 
and  potassium  compounds  have  been  principally  used,  being 
among  the  few  forms  soluble  in  water.  They  are  white 
powders,  not  volatile  at  a  red  heat. 

Detection  of  Preservatives. — Owing  to  the  difference  in 
the  chemical  character  of  preservatives  and  of  the  food  articles 
in  which  they  are  used,  few  general  methods  can  be  given  ; 
the  examination  must  be  conducted  with  reference  to  the 
material  likely  to  be  present.  The  following  are  suggestions 
in  this  direction  :  In  meats,  boric  acid  ;  in  milk  and  milk  prod- 
ucts, formaldehyde  and  boric  acid,  occasionally  salicylic  acid. 
In  jams,  jellies,  mince-meat,  and  table  delicacies,  benzoic  and 
salicylic  acids  or  their  salts  ;  occasionally  boric  acid.  In  cider 
and  some  other  fruit  juices,  salicylic  acid  and  sulfites.  In  fer- 
mented beverages  and  malt  extracts,  salicylic  acid,  sulfites, 
fluorids,  silicofluorids,  borofluorids  ;  abrastol  may  be  employed, 
but  the  data  in  regard  to  it  are  limited.  Saccharin  is  likely  to 
be  present  in  beers,  wines,  and  sweetened  articles. 

Benzoic  and  salicylic  acids  and  their  salts  may  often  be  de- 
tected by  shaking  the  material  with  a  mixture  of  equal  parts 
of  ether  and  petroleum  spirit.  A  little  sulfuric  acid  should  be 
added  if  the  material  is  not  already  distinctly  acid.  If  the  extrac- 


PRESERVATIVES  87 

tion  be  repeated  with  several  portions  of  the  solvent,  an  approxi- 
mate quantitative  determination  may  be  made.  The  shaking 
must  be  vigorous,  so  as  to  bring  the  solvent  in  contact  with  all 
parts  of  the  sample.  In  many  cases  this  will  produce  an  emul- 
sion which  separates  very  slowly.  The  application  of  the  cen- 
trifugal method  will  be  useful  in  this  case.  The  addition  of  more 
of  the  solvent  and  the  cooling  of  the  material  is  also  advised. 

The  following  descriptions  are  adapted  especially  to  the 
conditions  under  which  the  different  preservatives  are  likely 
to  be  found.  As  they  are  all  somewhat  soluble  in  water,  solid 
or  semi-solid  materials  may  be  exhausted  with  water  and  the 
liquid  concentrated  at  a  low  temperature.  In  many  cases  the 
sample  may  be  strained  through  muslin  and  the  tests  applied 
to  the  filtrate. 

The  volatility  of  some  preservatives,  especially  in  a  current 
of  steam,  is  occasionally  serviceable.  Formaldehyde  may  be 
thus  obtained  from  milk.  Benzoic  acid  and  saccharin  may  be 
separated  by  mixing  about  200  grams  of  the  sample  with  5  c.c. 
of  a  20  per  cent,  solution  of  phosphoric  acid,  and  distilling 
nearly  to  dryness.  The  benzoic  acid  distils,  while  the  saccha- 
rin remains  in  the  flask.  A  current  of  steam  passing  through 
the  distilling  flask  is  still  more  efficient. 

Salicylic  acid.  This  is  usually  detected  by  extraction  with 
an  immiscible  solvent  as  noted  above.  25  to  50  c.c.  of  the 
sample  are  rendered  feebly  acid  with  a  few  drops  of  sulfuric 
acid  and  shaken  vigorously  with  about  an  equal  bulk  of  a 
mixture  of  equal  parts  of  ether  and  petroleum  spirit,  the 
liquids  are  allowed  to  separate,  as  much  as  possible  of  the 
solvent  is  drawn  off,  filtered,  and  evaporated  at  a  gentle  heat. 
When  salicylic  acid  has  been  added  as  a  preservative,  distinct 
needle-like  crystals  will  be  usually  seen.  A  few  drops  of 
water  should  be  added  and  then  a  drop  of  ferric  chlorid  solu- 
tion. The  reaction  of  salicylic  acid  is  distinct.  When  a  crys- 
talline deposit  cannot  be  obtained,  a  larger  quantity  of  the 


88  FOOD    ANALYSIS 

sample  may  be  concentrated  at  a  gentle  heat  and  extracted  as 
above. 

Saccharin.  A  suitable  amount  of  the  sample  (50  or  100 
c.c.)  is  acidified  with  dilute  (25  per  cent.)  sulfuric  acid  and 
extracted  with  a  mixture  of  equal  parts  of  petroleum  spirit 
boiling  below  60°  and  ether.  The  solvent  is  evaporated  at  a 
gentle  heat.  The  presence  of  saccharin  in  the  residue  may 
be  detected  by  the  taste.  2  c.c.  of  a  saturated  solution  of 
sodium  hydroxid  are  added  and  the  dish  heated  until  the  residue 
dries  and  the  mass  fuses,  and  maintained  thus  for  half  an  hour. 
The  saccharin  is  converted  into  salicylic  acid,  which  may  be 
detected  in  the  residue  by  acidulating  it  with  sulfuric  acid  and 
applying  the  ferric  chlorid  test.  If  salicylic  acid  be  present 
originally  in  the  sample,  the  residue  from  the  petroleum  spirit 
and  ether  solution  is  dissolved  in  50  c.c.  of  dilute  hydrochloric 
acid,  bromin  water  added  in  excess,  the  liquid  shaken  well, 
and  filtered.  Salicylic  acid  is  completely  removed  as  a 
brominated  derivative.  The  filtrate  is  made  strongly  alkaline 
with  sodium  hydroxid,  evaporated,  and  fused  as  described 
above. 

Benzole  acid  and  benzoates.  E.  Mohler's  method  :  l  °  About 
100  grams  of  the  sample  are  made  alkaline  with  sodium 
hydroxid  and  evaporated  to  a  paste,  which  is  then  acidified 
with  hydrochloric  acid,  mixed  with  sand,  and  extracted  with 
ether.  The  ether  is  evaporated  spontaneously,  the  residue 
moistened  with  2  c.c.  of  sulfuric  acid,  heated  until  acid  vapors 
escape  (at  about  240°),  and  a  few  decigrams  of  sodium 
nitrate  added  in  small  portions,  until  the  liquid  becomes  color- 
less. The  liquid  is  poured  into  excess  of  ammonium  hydroxid 
and  a  drop  of  ammonium  sulfid  solution  added.  Benzoic  acid 
is  indicated  by  a  yellow,  changing  to  reddish-brown. 

Peter's  method  :  1 1  The  material  is  made  slightly  acid  and 
extracted  with  chloroform,  which  is  then  evaporated  sponta- 
neously. The  vessel  containing  the  residue  is  placed  in 


PRESERVATIVES  89 

melting  ice,  2  c.c.  of  sulfuric  acid  added,  and  stirred  until  the 
residue  is  dissolved.  Barium  dioxid  is  dusted  into  the  mass, 
with  constant  stirring,  until  the  liquid  begins  to  foam,  when  3 
c.c.  of  hydrogen  dioxid  (3  per  cent.)  are  added  drop  by  drop. 
The  dish  is  then  removed  from  the  cold  bath,  the  contents 
diluted  with  water  to  convenient  bulk,  and  filtered.  The  acid 
filtrate  is  extracted  with  chloroform.  The  benzoic  acid  will 
have  been  converted  into  salicylic  acid  by  the  process  and  the 
latter  may  be  detected  by  ferric  chlorid. 

Boric  acid  and  borax.  These  may  be  detected  in  many 
food-articles,  especially  milk  and  milk  products,  by  the  follow- 
ing test:  A  few  drops  of  the  sample  or  of  a  solution  obtained 
by  shaking  some  of  it  in  water  are  mixed  with  a  drop  of 
strong  hydrochloric  acid  and  a  drop  of  strong  alcoholic  solu- 
tion of  turmeric,  evaporated  to  dryness  at  a  gentle  heat,  and 
a  drop  of  ammonium  hydroxid  added  to  the  residue  when 
cold.  A  dull  green  stain  shows  that  boric  acid  is  present. 

Boric  acid  is  a  normal  constituent  of  wine,  and  hence  a 
qualitative  test  in  such  case  is  of  no  value.  The  following 
approximate  quantitative  test  is  recommended  by  W.  D.  Bige- 
low  :  A  series  of  solutions  containing  amounts  of  boric  acid 
from  o.ooi  to  0.020  gram  in  dilute  hydrochloric  acid  (i  part 
of  strong  acid  to  I  5  parts  of  water)  is  prepared.  A  drop  of 
each  solution  is  evaporated  on  a  piece  of  turmeric  paper  2  cm. 
square  and  the  color  noted,  care  being  taken  that  the  drops 
are  uniform.  50  c.c.  of  the  wine  are  made  slightly  alkaline 
with  calcium  hydroxid  solution,  evaporated  to  dryness,  and 
burned  to  an  ash.  3  c.c.  of  water  are  added  to  the  ash  and 
then  half-strength  hydrochloric  acid  drop  by  drop  until  the 
liquid  is  acid.  The  solution  is  then  made  up  to  5  c.c.  with 
hydrochloric  acid  one-sixth  the  strength  of  the  strong  acid, 
the  mass  mixed,  and  a  drop  tested  on  a  piece  of  turmeric 
paper  and  compared  with  the  standards.  If  stronger  than  a 


90  FOOD    ANALYSIS 

standard  which  is  of  characteristic  tint,  the  liquid  should  be 
diluted  with  the  I  to  i  5  hydrochloric  acid  and  again  tested. 

Fluorids.  100  grams  of  the  sample  are  made  slightly  alka- 
line with  ammonium  carbonate,  heated  to  boiling,  a  few  centi- 
meters of  calcium  chlorid  solution  added,  and  heating  con- 
tinued for  5  minutes.  The  precipitate  is  collected,  washed, 
dried,  transferred  to  a  platinum  crucible,  and  ignited.  When 
the  mass  is  cold,  a  few  drops  of  strong  sulfuric  acid  are 
added,  and  the  crucible  covered  with  a  piece  of  glass  partly 
protected  on  the  lower  side  by  paraffin.  The  bottom  of  the 
crucible  is  then  heated  for  an  hour  at  a  temperature  between 
75°  and  80°.  The  glass  is  etched  if  fluorids  are  present. 

Borofluorids  and  silicofluorids.  200  grams  of  the  sample 
are  made  alkaline  with  calcium  hydroxid  solution,  evaporated 
to  dryness,  incinerated,  and  the  ash  extracted  with  sufficient 
acetic  acid  to  decompose  carbonates.  The  residue  is  col- 
lected on  a  filter,  washed,  again  extracted  with  acetic  acid, 
and  filtered.  The  filtrate  contains  any  boric  acid  that  may  be 
present  and  is  tested  for  this  substance  as  directed  on  page 
89.  The  insoluble  residue  contains  the  calcium  silicate  and 
calcium  fluorid.  The  filter  and  residue  are  ashed,  a  portion 
of  the  mass  mixed  with  a  little  precipitated  silica  and  2  c.c. 
of  sulfuric  acid,  and  placed  in  a  short  test-tube  to  which  is 
attached  a  small  U-tube  containing  a  few  drops  of  water. 
The  test-tube  is  heated  cautiously  in  a  water-bath  ;  any  sili- 
con fluorid  that  may  be  formed  from  fluorin  present  will  pro- 
duce a  gelatinous  deposit  in  the  U-tube.  If  boric  acid  has 
been  found  in  the  filtrate  noted  above,  it  may  be  assumed  that 
any  fluorin  is  in  the  form  of  borofluorid  ;  but  if  boric  acid  is 
not  present,  the  other  portion  of  the  ash  from  the  filter  and 
residue  is  treated  with  sulfuric  acid  without  previous  addition 
of  silica.  If  gelatinous  silicic  acid  be  formed,  the  compound 
was  originally  silicofluorid. 

Formaldehyde.     The    tests    for    formaldehyde    have    been 


PRESERVATIVES  9! 

mostly  adapted  to  its  detection  in  milk.  It  is  not  likely  to 
be  used  as  a  general  food-preservative.  It  may  be  obtained 
pure  by  distillation  of  the  sample,  especially  in  a  current  of 
steam.  An  investigation  by  N.  Leonard,  H.  M.  Smith,  and 
H.  D.  Richmond  showed  that  with  ordinary  aqueous  solu- 
tions about  30  per  cent,  of  the  formaldehyde  has  passed  over 
when  20  per  cent,  of  the  liquid  has  been  distilled,  and  nearly 
50  per  cent,  when  40  per  cent,  of  the  liquid  has  been  dis- 
tilled. 

For  methods  of  detecting  formaldehyde  see  under0  Milk." 

For  detection  of  sulfites  see  under  "  Alcoholic  Beverages." 

fi-naphthol.     Several  allied  antiseptics   of  this  type  may  be 

detected  by  the  following  method  :   200  grams  of  the  sample 

are  acidified  with  sulfuric  acid  and  distilled  with  open  steam 

until  i  50  c.c.  of  distillate  are  obtained.     This  liquid  is  shaken 

with   20  c.c.    of  chloroform,  the  latter  withdrawn,   rendered 

alkaline  with  potassium  hydroxid,  and  heated  almost  to  boiling 

for  a  Tew  minutes.      Color  changes  occur  as  follows  : 

Salol,       light  red. 

Phenol, light  red,  to  brown,  to  colorless. 

3  naphthol, deep  blue,  to  green,  to  brown. 

A  portion  of  the  distillate  may  be  tested  as  follows  :  25  c.c. 
are  made  faintly  alkaline  with  ammonium  hydroxid,  then 
faintly  acid  with  nitric  acid,  and  a  drop  of  strong  sodium 
nitrate  solution  added.  /3-naphthol  develops  a  rose-color.  The 
reaction  is  rather  uncertain,  and  appears  to  be  affected  by 
light. 


SPECIAL  METHODS 

STARCH 
Detection. 

The  reaction  with  iodin  affords  a  delicate  method  for  detect- 
ing starch.  The  color  is  shown  by  the  undissolved  material, 
but  it  is  more  satisfactory  to  dissolve  it  by  boiling  with  water, 
allowing  the  solution  to  cool  and  adding  the  iodin,  preferably  as 
potassium  iodid-iodin  solution  (p.  35).  If  the  proportion  of 
starch  be  large,  an  almost  black  precipitate  will  be  formed. 
The  depth  of  color  will  be  some  indication  of  the  amount 
present,  but  exact  determinations  cannot  be  made  by  this 
method. 

In  the  undissolved  condition,  starch  may  be  recognized 
under  the  microscope  and  its  botanical  source  usually  deter- 
mined. A  magnifying  power  of  from  200  to  300  diameters 
will  be  required.  The  characteristics  of  the  granules  are  seen 
more  vividly  by  mounting  them  in  a  dense  medium  such  as 
chloral  hydrate  solution  or  glycerol  (p.  35)  and  arranging  the 
reflecting  mirror  so  as  to  throw  an  oblique  light  upon  the 
object.  By  this  means  distinct  markings,  termed  the  hilum 
and  concentric  rings,  are  recognized.  If  the  chloral-hydrate 
iodin  solution  (p.  35)  be  employed  for  mounting,  or  if  a  drop 
of  the  potassium  iodid-iodin  solution  be  introduced  under  the 
cover  of  a  glycerol  or  water  mounting,  the  granules  will 
become  blue. 

With  polarized  light,  many  starches  show  on  the  dark  field — 
i.  e.,  with  crossed  Nicols — dark  bands  radiating  from  the  hilum 
in  four  directions,  giving  the  appearance  of  a  Maltese  cross. 
For  this  examination  the  object  is  mounted  uncolored  in  one 
of  the  denser  media  and  the  light  thrown  directly  from  below. 

92 


STARCH  93 

By  inserting  a  selenite  plate  between  the  object  and  the  lower 
Nicol,  colors  will  be  produced  with  many  starches.  Muter 
employed  a  selenite  giving  a  green  field,  but  red  and  red-violet 
fields  are  also  suitable.  The  successful  application  of  these 
optic  methods  requires  good  apparatus  and  considerable  prac- 
tice. A  careful  study  of  starch-granules  of  authentic  origin 
should  always  be  made  before  deciding  as  to  the  nature  of 
any  specimen. 

A  synopsis  of  the  characters  of  the  principal  starches  is  pre- 
sented in  the  annexed  tables.  A  micron  (o.ooi  millimeter) 
may  be  converted  into  thousandths  of  an  inch  by  multiplying 
by  0.03937.  The  factor  0.04  will  be  near  enough  for  most 
cases.  The  classification  is  essentially  that  of  Muter,  the  basis 
being  the  predominating  form  of  the  granule,  the  distinctness 
and  position  of  the  hilum  and  markings,  the  appearance  under 
polarized  light,  with  or  without  selenite  plate.  Muter  indi- 
cated five  groups,  each  group  designated  by  the  name  of  an 
important  type  of  starch,  as  follows  : 

POTATO  GROUP. — Oval  or  ovate  granules,  showing  hilum 
and  concentric  rings  clearly,  cross  and  colors  usually  distinct. 

LEGUME  GROUP. — Round  or  oval  granules,  hilum  marked, 
rings  faint,  but  rendered  visible  in  cases  by  chromic  acid  solu- 
tion, cross  and  colors  feeble. 

WHEAT  GROUP. — Round  or  oval  granules,  hilum  and  rings 
generally  invisible,  feebly-marked  cross  and  colors. 

SAGO  GROUP. — Truncated  granules,  hilum  distinct,  faint 
rings,  cross  and  colors  fairly  marked. 

RICE  GROUP. — Polygonal  granules,  hilum  distinct,  rings 
faint,  cross  and  colors  usually  faint. 

In  the^  description  of  individual  starches,  the  term  "  eccen- 
tric "  denotes  that  the  hilum  is  not  in  the  apparent  center  of 
the  granule.  The  form  of  the  granule  is  usually  given  as 
oval,  spherical,  polygonal,  etc.,  terms  which  are  strictly  appli- 
cable to  surfaces  and  not  to  solids.  It  will  be  understood, 


94 


FOOD    ANALYSIS 


therefore,  that  such  terms  refer  to  the  apparent  cross-section 
of  the  granule  as  it  is  usually  viewed.  The  dimensions  given 
must  be  regarded  as  general  ;  granules  not  included  within 
the  limits  will  often  be  found.  Polarized  light  is  affected  to 
some  extent  by  almost  all  starch  granules,  if  very  close  ob- 
servation be  made. 


SIZE  IN 

GENERAL  CHARACTER 

WITH  Po 

LARIZER. 

MICRONS. 

OF  GRANULES. 

Without  Selenite. 

With  Selenite. 

Potato,     .    .    . 
Canna,     .    .    . 

60-100 
45-135 

Smaller  granules  round, 
large  ones  ovate  ;  hi- 
lum  a  spot,  eccentric  ; 
rings  numerous    and 
complete. 
Irregular  ovate  ;  hilum 
annular,  eccentric  ; 

Well-marked 
cross. 

Well-marked 
cross. 

Well-marked 
colors. 

Well-marked 
colors. 

Maranta, 


Natal     arrow- 
root, .    .    .    . 


Turmeric,   .    . 
Ginger,    .    .    . 

Mother-cloves, 
Banana,  .    .    . 


10-70 


35-40 

30-60 
40 

20-66 
40-80 


rings  incomplete, 
narrow  and  regular. 
Ovate ;  hilum  eccen- 
tric, circular  or  linear, 
often  cracked  ;  rings 
numerous,  not  very 
distinct ;  sometimes 
a  projection  at  one 
end. 

Ovate  to  circular,  ir- 
regular projections ; 
hilum  eccentric, 
cracked ;  rings  dis- 
tinct. 

Ovate,  often  much  nar- 
rowed at  one  end ; 
hilum  eccentric,  dot- 
like  ;  rings  indistinct. 

Ovate,  many  with  a 
projection  on  one  end ; 
hilum  and  rings 
scarcely  visible. 

Ovate  ;    hilum    a   dis-  ! 
tinct  spot,  eccentric  ; 
rings  visible. 

Ovate  but  often    very  ! 
narrow  in  proportion 
to    length;     hilum    a 
spot,  eccentric ;  rings 
distinct. 


Well-marked 
cross. 

Well-marked 
colors. 

Well-marked 
cross. 

Well-marked 
colors. 

Well-marked 
cross. 

Well-marked 
colors 

Faint  cross. 

Faint  colors. 

Well-marked 
cross. 

Well-marked 
colors. 

Faint  cross.         Faint  colors. 


STARCH 


95 


SOURCE. 

SIZE  IN 
MICRONS. 

GENERAL  CHARACTER 
OF  GRANULES. 

WITH  POLARIZER. 

Without  Selenite. 

With  Selenite. 

Bean,  .... 

35 

<enifonn     or     ovate  ; 

Cross  indistinct. 

Colors  very 

hilum  stellate  or  fur- 

faint. 

row-like  ;    rings  very 

faint. 

Pea,     .... 

'5-3° 

^eniform  or  ovate  ;  hi-   Cross  indistinct. 

Colors  very 

lum  elongated  ;  rings 

faint. 

very  faint. 

Lentil,     .    .    . 

3° 

^.eniform     or     ovate  , 

Dross  indistinct. 

Colors  very 

hilum  elongated,  dis- 

faint. 

tinct  ;  rings  visible. 

Nutmeg,     .    . 

5-5° 

bounded,  collected  in 

Cross  faint. 

Colors  very 

groups  of  two  to  four  ; 

faint. 

hilum  stellate  ;  rings 

invisible. 

Wheat,    .    .    . 

2-50 

VIostly  roundish,  chief- 

Cross not  well 

Colors  very 

ly    the   smallest   and 

marked. 

faint. 

largest  sizes  present  ; 

hilum  indistinct,  near- 

ly central  ;  rings   in- 

distinct. 

Barley,    .    .    . 

15-40 

Resembles  wheat   but 

Cross  not  well 

Colors  very 

some  granules  slightly 

marked. 

faint. 

( 

angular  or  elliptical  ; 

rings    more     distinct 

than  wheat. 

Rye,    .... 

20-60 

Resembles  wheat  ;   hi- 

Cross not  well 

Colors  very 

lum  distinct,  stellate; 

marked. 

faint. 

rings     often    visible. 

Distorted    forms    not 

infrequently  occur. 

Acorn,     .    .    . 

20 

Round  or   nearly  so  ; 

Cross  not  well 

Colors  not  well 

hilum  eccentric. 

marked. 

marked. 

Cacao,     .    .    . 

5-10 

Round  ;     hilum     and 

Cross  not  well 

Colors  not  well 

rings  indistinct. 

marked. 

marked. 

Sago,  .... 

25-66 

Ovate,  truncated  ;    hi- 

Well-marked 

Well-marked 

lum  a  circle  or  spot  ; 

cross. 

colors. 

rings  faint. 

Prepared  sago, 

Characters     less     dis- 

tinct    than     in     raw 

sago. 

| 

Tapioca,      .    . 

8-22 

Circular  ;  hilum  a  slit, 

Well-marked 

Well-marked 

nearly  central. 

cross. 

colors 

Prepared  tapi- 

oca,   .... 

Characters  less  distinct 

than  in  raw  form. 

Cinnamon, 

8-20 

Truncated  at  one  end, 

Well-marked 

Well-marked 

two  to  four  granules 

cross. 

colors. 

often   joined  ;    hilum 

di.>tinct,    nearly   cen- 

tral ;   rings  invisible. 

96 


FOOD    ANALYSIS 


SOURCE. 

SIZE  IN 
MICRONS. 

GENERAL  CHARACTER 
OF  GRANULES. 

WITH  POLARIZER. 

Without  Selenite. 

With  Selenite. 

Rice,    .... 

5-10 

Pentagonal,  hexagonal, 

Cross  distinct, 

Colors  distinct. 

occasionally    triangu- 

well marked. 

lar  with  sharp  angles  ; 

hilum  distinct  under 

high  power. 

Buckwheat,    . 

5-20 

Polygonal,        angles 

Cross  distinct. 

Colors  distinct. 

somewhat    rounded  ; 

hilum  central,  spot  or 

star  ;    granules   often 

compound. 

Oat,     .... 

5-30 

Mostly    polygonal,    a 

Faint  cross. 

Faint  colors. 

few  spherical  ;  hilum 

and  rings  visible  only 

* 

with      high     power  ; 

often  compound. 

Maize,     .    .    . 

5-20 

Round    to    polygonal, 

Faint  cross. 

Faint  colors. 

angles  usually  round- 

ed ;     hilum    central, 

crack  or  star;    rings 

nearly  invisible. 

Pepper,    .    . 

o-5-5 

Polygonal,  very  small,    Cross  with  high 

Color  with  high 

sometimes      showing           power. 

power. 

Brownian  movement, 

sometimes  united  into 

large  irregular  masses; 

hilum  only  seen  with 

high  power. 

(See  plates  in  Appendix. ) 

Determination. 

The  exact  quantitative  determination  of  starch  is  difficult. 
The  proposed  methods  have  been  carefully  investigated  by 
H.  W.  Wiley  and  W.  H.  Krug,  who  have  shown  that  in  the 
presence  of  vegetable  tissue  containing  pentosans  or  similar 
carbohydrates  the  diastase  method  is  alone  trustworthy.  The 
first  method  is  applicable  to  the  examination  of  commercial 
starches. 

HYDROCHLORIC  ACID  METHOD. — 3  grams  of  the  substance 
are  treated  with  about  50  c.c.  of  cold  water  for  an  hour,  with 
frequent  stirring ;  the  residue  is  collected  on  a  filter  and 
washed  with  sufficient  water  to  make  a  total  of  250  c.c.  This 


STARCH  97 

liquid  contains  the  soluble  carbohydrates.  The  undissolved 
residue  is  heated  for  2^  hours  with  2.5  per  cent,  hydro- 
chloric acid  (200  c.c.  water  and  20  c.c.  hydrochloric  acid,  sp. 
gr.  I..  125)  in  a  flask  provided  with  a  reflux  condenser,  cooled, 
neutralized  with  sodium  carbonate,  made  up  to  250  c.c., 
filtered,  and  the  dextrose  determined  in  an  aliquot  portion  of 
the  filtrate.  The  weight  of  dextrose  multiplied  by  0.9  gives 
the  weight  of  starch. 

DIASTASE  METHOD. — 3  grams  of  the  finely-powdered  sub- 
stance are  extracted  on  a  hardened  filter  with  five  successive 
portions  of  10  c.c.  of  ether,  washed  with  150  c.c.  of  a  10  per 
cent,  alcohol,  and  then  with  a  little  strong  alcohol.  The 
residue  is  mixed  in  a  beaker  with  50  c.c.  of  water.  The 
beaker  is  immersed  in  boiling  water,  the  contents  stirred 
constantly  until  all  the  starch  is  gelatinized,  cooled  to  55°, 
and  30  c.c.  of  malt-extract  added.  The  liquid  is  maintained 
at  55°  until  a  microscopic  examination  of  the  residue  shows 
no  starch  with  iodin.  It  is  cooled  and  made  up  directly  to  250 
c.c.  and  filtered.  200  c.c.  of  the  filtrate  are  placed  in  a  flask 
with  20  c.c.  of  a  25  per  cent,  solution  of  hydrochloric  acid  (sp. 
gr.  1.125),  connected  with  a  reflux  condenser,  and  heated 
in  boiling  water  for  2^/2  hours.  It  is  nearly  neutralized,  while 
hot,  with  sodium,  carbonate,  made  up  to  500  c.c.,  mixed, 
poured  through  a  dry  filter,  and  the  dextrose  determined  in 
an  aliquot  part.  Convert  the  dextrose  into  starch  by  the 
factor  0.9. 

Preparation  of  Malt  Extract. — 10  grams  of  fresh,  finely 
ground  malt  are  macerated  overnight  at  about  25°  with  200 
c.c.  of  water,  filtered,  the  amount  of  dextrose  in  a  given 
quantity  of  the  filtrate  after  boiling  with  acid  determined  as 
in  the  starch  determination,  and  the  proper  correction  noted. 
If  diastase  be  used,  a  correction  will  be  unnecessary.  A  good' 
diastase  is  now  easily  obtainable.  Commercial  malt  extracts 
are  liable  to  be  destitute  of  diastatic  power. 
9 


98  FOOD    ANALYSIS 

In  the  application  of  the  diastatic  method,  the  material 
must  be  ground  very  fine  and  the  preliminary  extraction  with 
ether  must  not  be  omitted.  In  many  cases  it  will  be  more 
convenient  to  make  the  extraction  in  the  continuous  extractor. 
If  a  large  tube  be  used,  several  samples  may  be  treated  at 
once  by  tying  each  in  filter-paper.  The  centrifugal  apparatus 
may  also  be  used.  The  fine  material  is  shaken  up  with  ether 
in  the  proper  tubes,  whirled  for  a  short  time,  the  ether  poured 
off,  fresh  ether  added  and  again  whirled,  and  the  operation  re- 
peated until  the  necessary  amount  of  solvent  has  been  used. 
The  liquid  may  be  poured  off  closely  each  time. 

FLOURS    AND    MEALS 

Meal  is  coarsely  ground,  flour  is  finely  ground  material. 
Most  of  the  forms  used  as  foods  are  derived  from  plants  be- 
longing to  the  order  Graminece,  but  buckwheat,  banana,  and 
potato  are  not  of  this  class.  The  distinction  between  the 
different  flours  and  meals  is  based  in  part  on  the  microscopic 
characters  of  the  starches  as  indicated  under  that  head,  but 
chemical  tests  are  in  some  cases  available.  The  proteids  of 
wheat  flour  have  been  studied  by  T.  B.  Osborne  and  E.  B. 
Voorhees.  The  most  important  are  gliadin  and  glutenin. 
Gliadin,  which  constitutes  nearly  half  the  proteid  matter  of 
the  grain,  is  soluble  in  dilute  alcohol.  Glutenin  is  insoluble 
in  water,  dilute  saline  solutions,  and  dilute  alcohol.  Gluten  is 
composed  of  gliadin  and  glutenin  in  nearly  equal  proportions. 
The  gliadin  forms  the  sticky  substance  of  the  gluten,  while 
the  glutenin  imparts  to  it  its  solidity.  Gluten  can  not  well  be 
formed  from  its  constituents  by  the  action  of  pure. water,  as 
gliadin  is  quite  soluble  in  that  menstruum  and  thus  is  easily 
removed.  The  mineral  salts  of  the  wheat,  however,  form 
with  distilled  water  a  medium  in  which  the  gliadin  is  scarcely 
soluble,  and  under  these  circumstances  the  gluten  is  produced. 

The   commercial   value   of  wheat  flour   depends   upon   its 


STARCH 


99 


color  and  texture  and  upon  quantity  and  quality  of  gluten. 
The  latter  differs  much  in  different  varieties  and  in  the  same 
variety  grown  in  different  localities.  In  whole- wheat  flour 
containing  about  10  per  cent,  of  gluten  the  quantities  of  the 
chief  proteids  are  about  as  follows  : 

Globulin, 0.70 

Albumin, 0.40 

Proteose, O-3O 

Gliadin, 4.25 

Glutenin,  ' 4.35 

Good  wheat  flour  will  yield  from  20  to  40  per  cent,  moist 
gluten  and  10  to  18  per  cent,  gluten  dried  at  100°.  Rye  flour 
contains  gliadin,  but  no  glutenin. 

COMPOSITION  OF  CEREAL  GRAINS 


WEIGHT 

OF  IOO 

KERNELS 
IN  GRAMS. 

MOIST- 
URE. 

6.25       ETHER 
N.      EXTRACT. 

CRUDE 
FIBER. 

ASH. 

CAR- 
BOHY- 
DRATES 

OTHER 
THAN 

CRUDE 
FIBER. 

Typical    unhulled 

barley,    

10.85 

II.  O 

2.25 

385 

2.5 

69-55 

Typical       American 

38.0 

10  75 

IO.O 

4.25 

1.75 

1.5 

71.75 

Typical  wheat,  .   .   . 

3-85 

10  6 

12.25 

1-75 

2.4 

1-75 

71-25 

Sweet  corn,  19  sam- 

ples (Richardson), 

8-44 

11.48 

8.57 

2.82 

1.97 

66.72 

Typical       American 
buckwheat  

3-0 

12.0 

10.75 

2.0 

10.75 

1-75 

62.75 

Typical  rye,     .... 

25 

10-5 

12.25 

1.5 

2.1 

1.9 

71-75 

Typical    unhulled 

oats,    

3-0 

IO.O 

12.  0 

4-5 

I2.O 

3-4 

58.0 

Tvpical    rice,    un- 

'hulled,    

3.0 

10.5 

7-5 

1.6 

9.O 

4.0 

67-4 

Typical  rice,  hulled, 

but  unpolished,  .   . 

2-5 

12.0 

8.0 

2.0 

1.0 

I.O 

76.0 

Typical     rice,     pol- 

ished .   . 

2.2 

12-4 

7-5 

0.4 

0.4 

0.5 

78.8 

Typical  rye  

2-5 

10.5 

12.25 

2.1 

1.9 

Typical  wheat,  .   .   . 

3-85 

10.6 

12.25 

1-75 

2-4 

i-75 

71-25 

A  detailed  description  of  the  proteid  and  other  constituents 
of  cereal  grains  has  been  published  by  the  United  States  De- 
partment of  Agriculture.  The  annexed  table  has  been  taken 


100  FOOD    ANALYSIS 

from  this.  The  proteids  are  calculated  by  multiplying  the 
nitrogen  by  the  factor  6.25,  but  the  investigations  by  T.  B. 
Osborne,  R.  H.  Chittenden,  and  E.  B.  Voorhees  indicate  that 
the  following  factors  would  be  better:  Maize,  6.23  ;  barley, 
rye,  and  wheat,  each  5.68  ;  oats,  6.10.  The  proteids  of  rice 
and  buckwheat  have  not  been  fully  studied.  A  recalculation  of 
the  proteids  by  corrected  factors  will  change  the  proportions  of 
the  carbohydrates,  since  these  were  determined  by  difference. 

Wheat  Flour. — Good  wheat  flour  is  a  fine  white  powder 
with  a  very  faint  yellow  tinge.  Several  tests  are  recognized 
for  its  examination,  among  which  are  the  following  : 

Color  Test. — The  sample  may  be  compared  with  one  of 
known  quality  by  laying  out  heaps  of  equal  size,  say,  3  cm. 
by  8  cm.,  and  0.5  cm.  deep.  If  this  be  done  on  a  colorless 
glass  plate,  the  examination  may  be  made  with  both  white 
and  colored  background,  and  the  plate  may  subsequently  be 
immersed  in  water  (not  over  35°)  so  that  the  colors  produced 
on  wetting  may  also  be  observed. 

Dougking  Test. — This  consists  in  making  a  dough  with  I  5 
grams  of  the  sample  and  10  c.c.  of  water  and  comparing  color, 
firmness,  elasticity,  and  compactness. 

Gluten  Test. — 10  grams  of  the  sample  are  mixed  with  suf- 
ficient water  to  make  a  stiff  dough  and  allowed  to  stand  for 
one  hour.  The  mass  is  kneaded  in  a  piece  of  linen  in  running 
water  until  the  washings  are  clear.  The  fresh  gluten  thus 
obtained  should  have  a  faint  yellow  tinge,  be  tough  and  of 
such  consistency  that  it  can  be  pulled  out  into  threads.  Gray 
and  red  glutens  indicate  inferior  samples.  Good  gluten  swells 
at  150°  and  assumes  the  appearance  of  bread. 

ADULTERATIONS.— Flour  may  be  mixed  with  mineral 
matters  to  increase  weight,  with  alum  or  copper  sulfate  to 
improve  its  appearance,  or  with  cheaper  flours  or  starches. 
It  may  also  contain  seeds  of  weeds,  may  be  damp  or  decom- 
posed, or  may  contain  fungi. 


STARCH 


101 


In  examining  for  these  adulterations,  determinations  of  ash, 
crude  fiber,  ether  extract,  and  total  nitrogen  are  of  consider- 
able value.  The  following  table  gives  some  data  on  these 
points,  but  the  limits  must  not  be  rigidly  interpreted.  The 
figures,  except  the  first  column,  have  been  calculated  on  the 
water-free  substance  : 

COMPOSITION   OF   FLOURS 


MOISTURE. 
Max.    Min. 

ASH. 
Max.    Min. 

6.25  N. 
Max.    Min. 

FIBER. 
Max.    Min. 

ETHER 
EXTRACT. 

Max.    Min. 

N-FREE 

EXTRACT. 
Max.    Min. 

Wheat,  .   .    . 
Rye  
Barlev 

15.0       9.0 

I4.O        12.0 

15  o     10  o 

0.8         0.3 
i-5         0.5 
20         i  o 

15.0       8.0 
u.o       6.0 

12  O          85 

I.O            O.I 

0.6         0.4 
06         03 

2.0             0.5 

i.o         0.9 

2O             O5 

90.0     82.0 
92.0      88.0 
92  o     87  o 

Buckwheat, 
Rice     .... 

18.0     12.5 
15.0     10  o 

1.5         0.8 
o  6         0.3 

9-5       5-0 
10  o       70 

0.6         0.3 
04         o  i 

2.0            0.8 
06          03 

93.0    84.0 
90  o     85  o 

Oat  (meal),     . 
Maize  (meal), 
Graham,    .   .    . 

10.0       6.0 
18.0       8.0 
15.0      u.o 

2.4            2.0 

4-5         i-o 

2.2              1.8 

18.0      14.0 
11.5       8.0 
15.0     10.0 

1.4         0.7 
3-5         0.7 

2.4             2.O 

9-5         6.5 
6.0         2.5 

2.2             1.9 

76.0     72.0 
80.0     63.0 
72.0     70.0 

ALUM. 

Logwood  Method. — An  alkaline  solution  of  logwood  is  pre- 
pared as  follows  :  Haifa  gram  of  fine  logwood  chips,  preferably 
freshly  cut  from  the  log,  is  macerated  for  10  hours  in  1 5  c.c.  of 
alcohol  ;  10  c.c.  of  the  solution  are  poured  off  and  mixed  with 
150  c.c.  of  water  and  10  c.c.  of  a  saturated  solution  of  am- 
monium carbonate.  To  make  the  test,  50  grams  of  the  flour 
are  made  into  a  thin  paste  with  water,  a  few  drops  of  the  log- 
wood solution  (freshly  prepared)  added,  and  the  mixture 
allowed  to  stand  several  hours.  Alum  produces  a  lavender- 
blue  lake. 

Cliloroform  Method. — 200  grams  of  flour  are  shaken  in  a 
separatory  funnel  with  a  sufficient  amount  of  chloroform, 
allowed  to  stand  overnight,  and  the  materials  which  subside 
carefully  removed  through  the  stopcock.  This  material  may 
be  further  purified  by  shaking  a  second  time  with  a  little  chlo- 
roform and  then  transferred  to  a  watch-glass  and  the  chloro- 


IO2  FOOD    ANALYSIS 

form  evaporated.  The  residue  is  treated  with  water,  the  solu- 
tion separated  from  the  insoluble  portion  and  allowed  to 
evaporate,  when  the  crystals  of  alum  will  be  observed.  The 
crystals  may  be  dissolved  in  water  and  tested  for  sulfates, 
aluminum,  potassium,  and  ammonium.  The  residue  insoluble 
in  water  should  be  examined  under  the  microscope  for  mineral 
matters.  The  steps  in  the  treatment  of  the  residue  insoluble 
in  chloroform  will  be  assisted  by  the  use  of  a  centrifuge. 

Copper  sulfate  can  be  detected  by  the  ferrocyanid  method  as 
described  under  BREAD. 

Ergot  in  Rye  Flour. — A  preliminary  test  may  be  made  to 
determine  if  the  flour  has  been  damaged  by  fungi.  Vogel 
advises  that  the  sample  be  stained  with  anilin  violet  and  exam- 
ined with  the  microscope.  Any  starch  granules  that  have 
been  injured  by  fungus  will  be  deeply  stained. 

M.  Gruber's  test :  A  little  of  the  flour  is  moistened  with 
water  on  a  microscope-slide,  a  cover-glass  placed  on,  and  the 
mass  heated  to  the  boiling-point  on  a  hot  plate  or  water-bath. 
After  cooling  it  is  examined  with  a  power  of  1 20  diameters. 
Ergot  will  be  recognized  by  its  high  refracting  power,  furrows, 
and  color — deep  violet  on  the  edge,  greenish-yellow  within. 
A  second  examination  with  a  power  of  about  300  diameters 
will  enable  any  doubtful  particles  to  be  recognized. 

Chemical  Tests. — 20  grams  of  the  sample  are  digested  with 
boiling  alcohol  as  long  as  any  color  is  extracted.  The  solu- 
tion is  treated  with  I  c.c.  of  sulfuric  acid  (i  13).  In  the 
presence  of  ergot  the  solution  will  be  red,  and  if  it  be  diluted 
with  a  large  volume  of  water,  the  color  may  be  extracted 
from  separate  portions  by  means  of  chloroform,  ether,  petro- 
leum spirit,  or  amyl  alcohol. 

10  grams  of  the  sample  are  macerated  for  about  30  minutes 
with  a  mixture  of  20  c.c.  of  ether  and  10  drops  of  dilute 
sulfuric  acid  (i  15);  the  liquid  filtered,  washed  with  ether 
until  the  filtrate  amounts  to  1 5  c.c.  This  is  shaken  with  5 


STARCH  IO3 

drops  of  a  saturated  solution  of  sodium  bicarbonate.  The 
chlorophyl  remains  in  the  ether  ;  the  sodium  bicarbonate  so- 
lution remains  clear  if  the  flour  be  from  sound  grain,  but 
takes  on  a  deep  violet  color  if  ergot  be  present. 

A.  Miller  examined  a  sample  of  flour  containing  not  more 
than  o.  i  per  cent,  of  ergot,  which  imparted  to  the  alcoholic 
extract  a  clear  rose  coloration  as  pronounced  as  if  the  propor- 
tion had  been  I  per  cent.  The  flour  contained  bluish-green 
particles  of  husk  of  unknown  origin,  which  assumed  a  red- 
dish tint  on  treatment  with  acidulated  alcohol,  and  imparted 
the  same  color  to  the  alcoholic  extract.  The  difference  in 
shade  between  the  color  produced  by  this  flour  and  one  con- 
taining ergot  was  only  distinguishable  in  concentrated  solu- 
tions, when  the  former  was  rose-red,  the  latter  brick-red. 

Mixed  Flours. — The  following  data  are  taken,  with  but  few 
changes,  from  the  contributions  of  Bigelow  and  Sweetser  and 
Kraemer  : 

Gluten  obtained  from  a  mixture  of  wheat  and  rye  flours  is 
dark  and  viscous,  without  homogeneity  ;  from  a  mixture  of 
wheat  and  barley  flours,  dark,  non-viscous,  and  dirty  reddish- 
brown  ;  from  a  mixture  of  wheat  and  oats,  dark  yellow  ;  from 
a  mixture  of  wheat  and  maize,  yellowish  and  non-elastic  ; 
from  a  mixture  of  wheat  and  leguminous  flour  it  varies  from 
a  grayish-red,  in  the  case  of  vetch  or  beans,  to  green,  in  the 
case  of  peas,  and  has  the  characteristic  odor  and  taste  of 
leguminous  products.  The  ash  of  leguminous  flour  is  deli- 
quescent, high  in  chlorids,  and  turns  turmeric  paper  brown  ; 
cereal  ash  is  the  reverse.  The  aqueous  extract  of  the  legu- 
minous flour  is  acid  ;  that  of  cereal  flour  is  faintly  alkaline. 
If  the  filtrate  from  the  gluten  determination  of  flour  contain- 
ing leguminous  flour  be  made  alkaline  with  ammonium  hy- 
droxid,  allowed  to  stand  overnight,  and  the  clear  liquid  de- 
canted, dilute  sulfuric  acid  will  precipitate  legumin. 


IO4  FOOD    ANALYSIS 

For  the  detection  of  potato  flour  a  portion  of  the  sample  is 
rubbed  in  a  mortar  until  a  stiff  paste  is  obtained,  thinned  with 
more  water,  filtered,  and  the  clear  filtrate  tested  with  a  drop  of 
a  dilute  solution  of  iodin.  Potato  flour  produces  a  deep  blue, 
while  with  pure  wheat  flour  the  result  is  yellow  or  light 
orange.  If  a  mixture  of  cereal  and  potato  flours  be  dried, 
spread  in  a  thin  layer  on  a  glazed  black  surface,  and  examined 
with  a  lens,  the  potato  is  indicated  by  bright  and  glassy  par- 
ticles in  the  otherwise  dull  white  substance. 

Vogel  extracts  the  flour  with  70  per  cent,  of  alcohol,  to 
which  5  per  cent,  of  hydrochloric  acid  has  been  added. 
The  extract  is  colorless  if  the  flour  consist  only  of  wheat  or 
rye,  pale  yellow  if  adulterated  with  barley  or  oats,  orange 
yellow  with  pea  flour,  purple  red  if  made  from  mildewed 
wheat,  and  blood  red  if  made  from  ergotized  wheat. 

Rice  in  Buckwheat  Flour. — When  pure  buckwheat  is  mixed 
with  water  into  a  thin  paste,  the  addition  of  calcium  hydroxid 
produces  a  dark  green,  which  becomes  red  when  acidified  with 
hydrochloric  acid.  Rice  flour  gives  a  yellow  color  with  potas- 
sium hydroxid  and  white  with  hydrochloric  acid.  A  mixture 
of  buckwheat  and  rice  flours  made  into  paste  is  changed  to  a 
light  green  color  by  potassium  hydroxid  and  becomes  flesh- 
colored  when  acidified  with  hydrochloric  acid. 

Wheat  in  Rye  Flour. — A.  Kleeburg  has  advised  the  follow- 
ing test :  A  pinch  of  the  sample  is  mixed  on  a  small  glass 
plate  (a  microscope-slide  will  serve)  with  water  at  about  45° 
in  sufficient  quantity  that  the  particles  of  flour  still  float.  The 
mixture  is  spread  over  a  considerable  part  of  the  glass  and  a 
similar  glass  laid  upon  it  so  that  about  one-fourth  of  each 
glass  protrudes  at  the  ends.  The  two  glasses  are  pressed 
together,  the  exuded  liquid  wiped  off,  and  the  glasses  rubbed 
on  each  other  several  times.  If  wheat  flour  be  present,  white 
spots  will  be  observed,  which  will  form  threads  on  being 
rolled  ;  these  are  short  and  thin  if  the  proportion  of  wheat  be 


STARCH  IO5 

small,  and  thicker  and  longer  with  larger  amounts.  An  ad- 
mixture of  5  per  cent,  of  wheat  flour  with  rye  is  said  to  be 
thus  recognizable. 

Maize  in  Wheat  Flour. — H.  Kraemer  has  devised  the  follow- 
ing test,  which,  he  states,  will  detect  5  per  cent,  of  maize  in 
wheat  flour  :  I  gram  of  the  sample  is  mixed  with  I  5  c.c.  of 
good  glycerol  and  heated  to  boiling  for  a  few  minutes.  An 
odor  recalling  that  of  popcorn  indicates  maize. 

It  is  alleged  that  cheap  flours  have  been  adulterated  with 
sawdust.  G.  A.  Le  Roy  applied  the  following  test  for  detect- 
ing this  addition  :  A  small  amount  of  the  sample  is  gently 
warmed  with  the  acid  solution  of  phloroglucol  (page  35). 
Ordinary  wood-fiber  quickly  acquires  a  bright  red  tint,  while 
bran  particles  are  but  slightly  affected. 

BREAD 

Bread  is  made  by  baking  the  mass  obtained  by  kneading 
flour  with  water.  This  gives  the  so-called  unleavened  bread, 
but  it  is  usual  to  add  a  little  common  salt  to  the  water  and 
make  the  dough  light  by  inflating  it  with  carbon  dioxid.  This 
may  be  done  by  the  use  of  baking  powder,  or  by  mixing  the 
flour  with  water  containing  carbonic  acid  under  pressure  (aer- 
ated bread),  but  commonly  yeast  is  added  to  the  dough  and 
the  mixture,  called  the  "  sponge,"  allowed  to  stand  for  some 
hours  and  then  baked.  The  slight  fermentation  which  occurs 
liberates  carbon  dioxid. 

The  chemical  composition  of  bread  is  approximately  that  of 
the  flour  from  which  it  is  made.  The  moisture  usually  ranges 
from  30  to  40  per  cent.,  and  will  depend,  among  other  condi- 
tions, upon  the  quantity  and  quality  of  the  gluten,  and  the 
size  and  shape  of  the  loaf.  On  the  size  and  shape  will  also 
depend  the  relative  proportion  of  crust  to  crumb,  the  latter 
containing  about  twice  as  much  moisture  as  the  former.  The 
addition  of  potato  flour  or  rice  flour  will  enable  a  bread  to  be 

10 


io6 


FOOD    ANALYSIS 


prepared  containing  a  much  larger  proportion  of  water  than 
usual.  The  addition  of  about  I  per  cent,  of  mashed  potatoes 
to  the  dough  is  said  to  render  the  bread  white  without  any 
notable  increase  in  the  amount  of  moisture  retained. 

The  proportion  of  fat  in  bread,  as  determined  by  the  ether 
extract,  is  apt  to  be  less  than  that  of  the  original  flour,  owing 
to  decomposition  of  the  fat  in  the  crust,  by  heat,  and  also  to 
the  inclosure  of  the  fat  particles  in  such  a  way  as  to  render 
them  difficult  of  extraction.  On  the  other  hand,  the  propor- 
tion of  fatty  matter  may  be  increased  by  the  use  of  milk  or  by 
the  material  used  to  grease  the  pans. 

When  bread  is  raised  by  yeast,  some  solid  matter  is  lost  by  the 
fermentation.  According  to  Lawes  and  Gilbert,  this  is  prob- 
ably less  than  ^  of  I  per  cent.,  and  appears  to  be  due  to  the 
decomposition  of  the  sugar.  The  unchanged  starch  is  not 
appreciably  altered  during  the  short  time  that  the  yeast  acts. 
The  ash  of  bread  will  be  higher  than  that  of  the  flour  if  salt 
or  baking  powder  has  been  added. 


ORIG- 

INAL 
SUB- 

IN THE  DRY  SUBSTANCE. 

STANCE 

Carbo- 

Moist- 
ure. 

Pro- 
teids, 
NX 

Ether 
Ex- 
tract. 

Crude 
Fiber. 

Ash. 

Salt. 

hy- 
drates. 
exclud- 

5-70. 

ing 

Fiber. 

Vienna,  average  of  10  sam- 

ples. 

?g  71 

13  21 

I  Tl 

O  Q7 

I  Q$ 

O  Q3 

8^  I 

Home-made,  average  of  2 

y*'  i  » 

J'^O 

*••  1  3 

•*•  yl 

••  yy 

vy'  yj 

WO 

samples,   

33-02 

10.8 

2.9I 

0.36 

i-55 

0.84 

84.75 

Graham,  average  of  9  sam- 

ples 

•\A    g 

12  ci 

3    13 

I  74. 

2.2Q 

I.  O7 

82.06 

Rye,  average  of  7  samples, 

oH-><j 
33-42 

»*»3« 

11.86 

JO 
I.  O2 

*•  /  *fr 

0-95 

*>,+y 

2-79 

•  •w^ 

1.5 

84.36 

Quaker,  average  of  3  sam- 

ples,       

36.16 

11.17 

!-75 

0.41 

1.68 

0.92 

85.41 

Miscellaneous,   average   of 

9  samples,    ..... 

34-41 

10.59 

2.21 

0.46 

i-53 

0.76 

85.66 

BREAD  ID/ 

The  table  on  page  106  represents  the  average  composition 
of  various  breads  of  commerce  according  to  analyses  made  in 
the  laboratory  of  the  United  States  Department  of  Agricul- 
ture. The  loaves  weighed  approximately  one  pound  each. 
Trade  names  are  given  in  most  cases. 

ADULTERATIONS. — These  may  consist  in  the  use  of  damaged 
flour,  of  flours  other  than  that  purporting  to  be  present, 
presence  of  excess  of  water,  or  addition  of  alum  or  copper 
sulfate  to  improve  appearance. 

ALUM. — ^The  bread  is  moistened  with  water  and  some  of 
the  alkaline  logwood  solution  (see  p.  101).  If  alum  be 
present,  the  bread  will  become  lavender-blue  in  an  hour  or 
two.  Pure  bread  assumes  a  light  red-brown  tint.  The  blue 
color,  however,  is  not  proof  of  the  presence  of  alum  unless 
it  is  permanent  at  the  temperature  of  boiling  water. 

Blyth's  test  for  alum  is  as  follows  :  1 50  grams  of  the  material 
are  macerated  for  two  days  in  2  liters  of  water.  The  solution 
is  strained  through  muslin  and  evaporated  at  a  gentle  heat  to 
small  volume  ;  a  strip  of  gelatin  immersed  in  this  liquid,  and 
then  in  the  alkaline  logwood  solution,  will  acquire  the  laven- 
der color  if  alum  is  present  to  the  extent  of  0.03  per  cent. 

These  tests  are  not  applicable  to  sour  bread.  J.  Vander- 
planken  recommends  the  following  modification  to  meet  the 
difficulty  :  I  5  grams  of  the  sample  are  triturated  to  a  paste 
with  water  and  some  pure  sodium  chlorid  and  10  drops  of 
a  freshly-prepared  solution  of  logwood  in  alcohol,  and  then 
5  grams  of  pure  potassium  carbonate  are  added.  The  mass  is 
well  mixed,  washed  with  100  c.c.  of  water  into  a  beaker,  and 
is  allowed  to  settle.  In  a  few  minutes  the  liquid  becomes 
reddish-violet  if  alum  is  absent,  grayish-blue  to  deep  blue 
when  it  is  present. 

The  quantitative  estimation  of  the  alum  is  made  as  follows  : 
The  ash  from  100  grams  or  more  of  the  bread  is  boiled  with 
hydrochloric  acid  and  the  solution  filtered.  The  filtrate  is 


108  FOOD    ANALYSIS 

boiled  and  added  to  a  concentrated  solution  of  sodium  hy- 
droxid,  the  mixture  being  again  boiled  and  filtered  while  hot. 
A  little  disodium  acid  phosphate  is  added  to  the  filtrate,  which 
is  then  slightly  acidulated  with  hydrochloric  acid  and  finally 
made  feebly  alkaline  by  addition  of  ammonium  hydroxid.  The 
precipitate  of  aluminum  phosphate  is  filtered,  washed,  ignited, 
and  weighed.  Flour  contains  a  small  proportion  of  aluminum, 
which,  in  the  ash,  is  probably  in  the  form  of  silicate.  The 
amount  of  silica  is  approximately  equal  to  that  of  alum  equiva- 
lent to  the  aluminum  normally  present.  It  is  the  practice, 
therefore,  to  determine  the  silica  and  subtract  it  from  the 
amount  of  alum  calculated  from  the  aluminum  phosphate 
found.  The  remainder,  multiplied  by  4.48  or  3.73,  will  give 
the  potassium  alum  or  ammonium  alum  respectively. 

Copper  sulfate  may  be  detected  by  the  brown  produced 
when  a  thin  slice  of  bread  is  immersed  in  a  dilute  solution  of 
potassium  ferrocyanid. 

Foreign  flours  may  be  sought  for  by  the  microscope,  but 
the  starch  granules  are  often  so  altered  by  heat  as  to  render 
their  identification  impossible. 

The  following  adulterants  are  said  to  be  employed  abroad, 
but  their  use  does  not  appear  to  have  been  attempted  in  this 
country  : 

Soap  is  said  to  be  used  to  render  the  bread  light  and  soft. 
It  is  said  to  be  added  in  solution  containing  emulsified  oil. 

Terra  alba  and  gypsum  have  been  found ;  they  are  readily 
detected  in  the  ash. 

Stannous  chlorid  is  a  common  constituent  of  ginger  cake,  to 
which  it  is  added,  with  potassium  carbonate,  in  order. to  give 
the  product  the  color  ordinarily  produced  by  honey  or  mo- 
lasses. It  is  said  to  render  a  product  made  of  poor  flour  and 
molasses  of  the  same  color  as  that  produced  by  a  good  flour 
and  honey.  Tin  may  be  detected  as  described  on  page  69. 


LEAVENING    MATERIALS 


LEAVENING  MATERIALS 

The  yeast  cakes  sold  for  leavening  purposes  are  usually 
mixtures  of  common  yeast  with  potato  starch.  The  study 
of  yeast  is  practically  limited  to  those  connected  with  the 
fermentation  industries.  Cream  of  tartar  and  baking  soda  are 
commonly  employed  as  leavening  agents. 

Baking  Soda,  Sodium  Acid  Carbonate,  is  not  subject  to 
serious  adulteration. 

Cream  of  Tartar,  Acid  Potassium  Tartrate,  is  frequently 
adulterated  with  starch,  alum,  acid  calcium  phosphate,  calcium 
sulfate,  and  potassium  acid  sulfate.  Many  samples  will  be 
found  to  contain  no  tartrate,  but  merely  a  mixture  of  starch, 
calcium  phosphate,  and  alum. 

A.  H.  Allen  has  devised  the  following  method  for  the  ex- 
amination of  commercial  cream  of  tartar  : 

1.  88  1  grams  of  the  dried  material  are  dissolved  in  hot  water 
and  titrated  with  *  sodium  hydroxid  arid  phenolphthalein. 
If  tartaric  acid  and  acid  sulfates  are  not  present,  each  c.c. 
will  represent  I  per  cent,  of  acid  potassium  tartrate. 

i.  88  1  grams  of  dried  material  are  ignited  for  10  minutes, 
the  residue  boiled  with  water,  filtered,  and  washed.  The 
filtrate  is  titrated  with  ^  hydrochloric  acid  and  methyl-orange. 
With  pure  tartrate  the  amount  of  acid  consumed  will  be  the 
same  as  that  of  the  alkali  in  the  first  experiment.  Each 
cubic  centimeter  of  deficiency  is  equivalent  to  0.36  per  cent. 
calcium  sulfate,  or  0.72  per  cent,  acid  potassium  sulfate.  If 
the  amount  of  acid  be  more  than  equivalent  to  that  of  the 
alkali  used  in  the  former  experiment,  it  suggests  the  presence 
of  neutral  tartrate,  each  cubic  centimeter  of  excess  represent- 
ing 0.6  per  cent,  thereof.  The  amount  of  sulfate  can  be  de- 
termined by  precipitating  with  barium  chlorid  in  the  usual 
way. 

The  residue  is  ignited,  dissolved  in  20  c.c.  of  io  acid,  filtered 


I  10 


FOOD    ANALYSIS 


from  any  insoluble  residue,  and  the  filtrate  titrated  with  ^ 
alkali.  Each  c.c.  corresponds  to  0.5  per  cent,  of  calcium 
tartrate,  or  0.36  per  cent,  of  anhydrous  calcium  sulfate. 

The    cream  of  tartar  substitutes    commonly  sold    contain 
starch,  alum,  and  calcium  phosphate.     The  presence  of  starch 


FIG.  37. 

and  its  source  can  easily  be  determined  by  the  iodin  test  and 
microscopic  examination.  Quantitative  examination  of  such 
samples  will  be  conducted  as  described  under  "  Baking  Pow- 
ders." 

Baking  Powders. — These  contain  acid  sodium  carbonate, 
some  acid    salt,   e.  g.,  acid  potassium  tartrate,  acid  calcium 


LEAVENING    MATERIALS  1 1  i 

phosphate,  or  alum,  with  inert  material,  starch  or  flour,  to 
prevent  caking.  Many  powders  contain  both  alum  and  acid 
calcium  phosphate.  The  following  methods  for  examining 
baking  powders  were  published  by  C.  A.  Crampton  :  1 2 

The  value  of  baking  powder  depends  on  the  gas  liberated 
when  it  is  mixed  with  water.  The  determination  may  be  made 
by  the  apparatus  arranged  by  A.  E.  Knorr. 13  (Fig.  37.)  The 
flask  A  holds  the  weighed  portion  of  sample.  The  condenser 
D,  attached  by  a  ground  joint,  serves  to  condense  the  steam 
formed  when  the  liquid  in  A  is  boiled.  ~B  contains  either 
recently-boiled  water  or  dilute  sulfuric  acid,  according  to 
whether  the  available  carbon  dioxid  or  total  carbonates  are  to 
be  determined. 

It  has  a  soda-lime  .tube  attached  by  a  ground-joint  to  pre- 
vent admission  of  carbon  dioxid  from  the  current  of  air  which 
is  drawn  through  the  apparatus  during  the  operation.  The 
junction  of  this  portion  with  the  flask  should  be  by  ground 
or  fused  joint.  The  evolved  gas  is  dried  in  E  by  sulfuric 
acid  and  absorbed  in  F. 

Available  carbon  dioxid,  which  gives  the  leavening  power, 
is  determined  as  follows  :  The  flask  A  is  dried  thoroughly, 
a  weighing  tube  is  charged  with  about  2  grams  of  the  powder, 
accurately  weighed,  the  contents  emptied  into  the  flask,  and 
the  tube  weighed  again.  The  exact  amount  of  powder  taken 
is  thus  known.  Recently-boiled  water  is  put  into  B,  the 
apparatus  connected  tightly,  and  the  water  allowed  to  flow  in 
slowly  from  B,  the  aspirator  attached  to  G  being  put  in 
operation.  When  the  effervescence  in  A  has  ceased,  the 
liquid  in  it  is  boiled  for  a  few  seconds,  the  lamp  removed, 
and  aspiration  through  G  continued  for  15  minutes.  The 
absorption  apparatus  F  is  weighed,  and  the  increase  represents 
carbon  dioxid.  Total  carbonates  are  determined  by  substi- 
tuting 10  c.c.  dilute  sulfuric  acid  for  the  water  in  B. 

Starch. — 5   grams  are  mixed  in  a   flask    with   200  c.c.  of 


I  12  FOOD    ANALYSIS 

4  per  cent,  hydrochloric  acid.  A  condensing  tube  about  I 
meter  long  is  attached  by  means  of  a  cork  (an  inverted  con- 
denser may  be  used)  and  the  liquid  boiled  for  4  hours.  The 
contents  are  cooled,  rendered  slightly  alkaline  by  sodium  hy- 
droxid,  and  the  dextrose  determined  as  given  under  "  Sugars," 
and  multiplied  by  0.9. 

For  powders  not  containing  appreciable  amounts  of  alum, 
direct  washing  with  water,  and  drying  the  residue,  will  often 
give  determinations  of  sufficient  accuracy.  Since  the  residual 
liquid  in  properly-made  baking  powders  is  alkaline,  due  to 
slight  excess  of  baking  powder,  the  diastase  method  for  starch 
may  be  applicable.  The  liquid  should  be  filtered  and  the 
insoluble  residue  well  washed.  The  aluminum  hydroxid  may 
interfere  with  this  method.  If  flour  be  used  as  filler,  which 
may  be  ascertained  by  inspection,  the  starch  found  may  be 
roughly  calculated  to  flour  by  the  tables  on  page  99. 

Aluminum  and  Phosphates. — K.  P.  McElroy  1 4  devised  the 
following  method  :  5  grams  are  charred  in  a  platinum  basin, 
mixed  with  strong  nitric  acid,  and  filtered  into  a  500  c.c.  flask. 
The  residue  is  washed  slightly,  the  filter  and  residue  returned 
to  the  basin,  burned  to  whiteness,  mixed  with  sodium  carbon- 
ate, fused,  and  cooled.  Nitric  acid  is  added,  the  liquid  evapo- 
rated to  dryness,  again  acidified  with  nitric  acid,  and  the  whole 
mass  washed  into  the  500  c.c.  flask.  The  liquid  is  made  up  to 
the  mark  and  filtered  through  a  dry  filter,  100  c.c.  of  the 
filtrate  are  nearly  neutralized  with  ammonium  hydroxid,  am- 
monium nitrate  and  ammonium  molybdate  solution  added, 
the  mass  digested  at  a  low  heat  for  a  few  hours,  and  filtered. 
The  filtrate  contains  the  aluminum,  which  may  be  precipitated 
as  hydroxid  by  adding  ammonium  hydroxid.  The  precipitate  is 
dissolved  in  ammonium  hydroxid  and  the  phosphate  deter- 
mined in  the  usual  way. 

Calcium. — 5  grams  are  mixed  in  a  500  c.c.  flask  with  50 
c.c.  of  water  and  30  c.c.  of  strong  hydrochloric  acid,  the 


SUGARS  I  I  3 

mixture  made  up  to  the  mark,  shaken  well,  and  allowed  to 
settle.  50  c.c.  are  collected  through  a  dry  filter,  nearly  neu- 
tralized by  ammonium  hydroxid,  acetic  acid  added  in  small 
amount,  then  ammonium  acetate,  and  the  liquid  boiled.  If 
any  precipitate  forms  it  should  be  removed.  The  clear  liquid 
is  precipitated  by  ammonium  oxalate. 

Sulfates. — 0.5  gram  of  the  sample  are  digested  with  strong 
hydrochloric  acid  until  everything  has  dissolved,  the  liquid  is 
diluted  considerably,  brought  to  boiling,  and  precipitated  with 
barium  chlorid,  taking  care  not  to  use  a  large  excess.  The 
precipitate  is  weighed  in  the  usual  manner. 

Ammonium  Compounds, — These  may  be  determined  by  the 
Kjeldahl-Gunning  method  applied  to  the  water  filtered  from 
a  known  weight  of  the  powder. 

The  best  commercial  baking  powders  yield  about  12  per 
cent,  by  weight  of  gas.  10  grams  would,  therefore,  yield  1.2 
grams,  occupying  at  ordinary  temperature  about  600  c.c., 
which  will  be  much  increased  in  baking.  Many  powders 
yield  much  less  gas. 

SUGARS 
Detection. 

Most  of  the  tests  for  sugars  depend  on  their  reducing  effect, 
except  the  phenylhydrazin,  fermentation,  and  optic  tests.  Su- 
crose possesses  less  reducing  action  than  other  common  sugars, 
does  not  give  any  precipitate  with  phenylhydrazin,  and  is  not 
directly  fermentable.  By  the  action  of  dilute  acids  or  inver- 
tase  (yeast-enzym)  it  is  converted  into  equal  parts  of  dextrose 
and  levulose,  a  change  commonly  termed  "  inversion,"  the  mix- 
ture being  known  as  "invert-sugar."  This  responds  to  all 
the  above  tests. 

Cobalt  Nitrate  Test. — Wiley  has  experimented  with  this 
method  and  has  obtained  satisfactory  results.  He  describes 
it  as  follows  : 


114  FOOD    ANALYSIS 

5  c.c.  of  a  5  per  cent,  solution  of  cobaltous  nitrate  are  well 
mixed  with  15  c.c.  of  sugar  solution,  and  2  c.c.  of  a  50  per 
cent,  solution  of  sodium  hydroxid  added.  Sucrose  gives  an 
amethyst-violet  solution,  which  is  made  somewhat  more  blue 
by  boiling,  but  regains  its  color  on  cooling.  Dextrose  gives 
a  turquoise-blue,  which  in  the  course  of  two  hours  passes  into 
a  pale  green.  A  slight  flocculent  precipitate  is  noticed  in  the 
tube  containing  dextrose.  Maltose  and  lactose  act  very  much 
as  dextrose,  but  in  the  end  do  not  give  so  fine  a  green  color. 
If  the  solution  containing  dextrose,  lactose,  or  maltose  be 
boiled,  the  original  color  is  destroyed  and  a  yellow-green 
color  takes  its  place.  In  mixtures  of  dextrose  and  sucrose 
the  sucrose  coloration  predominates — one  part  of  sucrose  in 
nine  parts  of  dextrose  can  be  distinguished.  Impurities  such 
as  gum  arabic  or  dextrin  should  be  removed  by  alcohol  or 
lead  subacetate  before  the  application  of  the  test.  Dextrin 
may  also  be  thrown  out  by  treatment  of  the  solution  with 
barium  hydroxid  and  ammoniacal  lead  acetate.  The  reaction 
may  be  applied  to  the  detection  of  cane-sugar  in  wines  after 
they  are  thoroughly  decolorized  by  means  of  lead  acetate  and 
bone-black.  Sucrose  may  be  detected  in  fresh  or  condensed 
milk  after  the  disturbing  matters  have  been  thrown  out  by 
lead  acetate.  Sucrose  may  be  detected  in  honey. 

Phenylhydrazin  Test. — Phenylhydrazin  hydrochlorid  is  usu- 
ally employed.  The  commercial  article  is  often  contaminated 
with  anilin  hydrochlorid.  It  may  be  purified  by  solution  in  hot 
water,  precipitation  by  strong  hydrochloric  acid,  and  recrys- 
tallization  from  hot  water. 

For  the  test,  o.  I  gram  of  the  sample,  about  0.2  gram  phenyl- 
hydrazin  hydrochlorid,  and  0.3  gram  of  sodium  acetate  are 
dissolved  in  5  c.c.  of  water  and  heated  on  the  water-bath  for 
some  time.  Sucrose  forms  no  precipitate,  but  with  many 
sugars  crystalline  compounds  called  osazones  separate. 

Dextrosazone  and  levulosasone  have  similar  properties,  crys- 


SUGARS  I  I  5 

tallizing  in  needles  melting  at  204°— 205°.  They  reduce  Fehl- 
ing's  solution,  and  when  dissolved  in  acetic  acid  are  slightly 
levorotatory. 

Maltosazone  crystallizes  in  tables,  which  melt,  with  decom- 
position, at  206°.  It  is  levorotatory. 

Lactosazone  crystallizes  in  prisms  of  melting-point  200°. 

Sucrose  forms  no  osazone.  After  inversion  it  yields  a  mix- 
ture of  dextrosazone  and  levulosazone. 

Lactose,  after  boiling  with  sulfuric  acid,  yields  a  mixture  of 
dextrosazone  and  galactosazone.  The  latter  is  distinguished 
by  its  melting-point,  193°,  from  dextrosazone. 

Starch  and  dextrin,  after  hydrolysis,  yield  dextrosazone  and 
maltosazone. 

The  application  of  these  reactions  to  the  quantitative  deter- 
mination of  sugars  has  met  with  partial  success. 

Determination. 

.  The  preparation  of  sucrose  for  use  as  a  standard  in  polar- 
imetry  and  reduction-tests  has  been  the  subject  of  formal  action 
at  the  third  session  of  the  International  Commission  for  Uni- 
form Methods  of  Sugar  Analysis,  Paris,  July  24,  IQOO.15 

Purest  commercial  sugar  is  selected  and  dissolved  by  satu- 
ration in  hot  water,  and  ethyl  alcohol  added  sufficient  to  pre- 
cipitate the  sugar.  The  precipitate  is  whirled  in  a  centrifuge 
and  washed  with  alcohol.  The  material  obtained  is  put  through 
the  whole  process  a  second  time,  and  the  washed  material  is 
dried  on  pure  bibulous  paper  and  kept  in  stoppered  glass  ves- 
sels. It  still  contains  moisture,  which  must  be  determined 
and  allowed  for  in  making  standard  solutions. 

The  temperature  of  the  water  is  not  given.  Blotting-paper 
is  mentioned  in  the  text,  but  folds  of  pure  filter-paper  seem 
best,  as  commercial  blotting-paper  is  of  uncertain  composition. 

For  the  standardization  of  solutions  for  the  determination  of 
sucrose  and  invert-sugar,  2.5  grams  of  pure  sucrose  should 


Il6  FOOD    ANALYSIS 

be  dissolved  in  a  mixture  of  75  c.c.  of  water  and  5  c.c.  of 
hydrochloric  acid  (sp.  gr.  1.188  at  15°),  inverted  according 
to  the  method  on  page  1 24,  the  acid  neutralized  with  sodium 
carbonate,  and  the  solution  diluted  to  one  liter.  2.5  grams  of 
sucrose  yield  2.6316  grams  of  invert-sugar.  The  number  of 
cubic  centimeters  of  sugar  solution  used,  multiplied  by 
0.00263,  will  give  the  weight  of  invert-sugar  required  to  re- 
duce completely  10  c.c.  of  the  test  solution  under  the  con- 
ditions of  the  experiment. 

CHEMICAL  METHODS. 

The  following  standard  reagents  are  generally  employed  : 
SOXHLET'S  MODIFIED  COPPER  SOLUTION  (A.  o.  A.  c.). 

Copper  sulfate  solution.  34.639  grams  of  pure  crystallized 
copper  sulfate  are  dissolved  in  sufficient  water  to  make  500 
c.c. 

Alkaline  tartrate  solution.  173  grams  of  pure  potassium 
sodium  tartrate  and  50  grams  of  sodium  hydroxid  are  dis- 
solved in  sufficient  water  to  make  100  c.c.  A  convenient 
method  is  to  use  100  c.c.  of  a  solution  containing  500  grams 
of  sodium  hydroxid  in  one  liter.  Potassium  acid  tartrate,  now 
obtainable  of  very  good  quality,  may  be  used  instead  of  potas- 
sium sodium  tartrate,  in  which  case  the  proportion  required 
will  be  133  grams  of  potassium  acid  tartrate  and  80  grams  of 
sodium  hydroxid  made  up  to  500  c.c.  The  copper  and  alka- 
line tartrate  solutions  must  be  kept  separate  in  well-stoppered 
bottles  and  mixed  only  when  needed. 

APPROXIMATE  VOLUMETRIC  METHOD  FOR  RAPID  WORK. 

5  c.c.  of  each  of  the  solutions  are  placed  in  a  large  test-tube, 
10  c.c.  of  distilled  water  added,  the  liquid  heated  to 'boiling, 
and  small  portions  of  the  solution  to  be  tested  gradually  added 
until  the  copper  has  been  completely  precipitated,  boiling  to 
complete  the  reaction  after  each  addition.  When  the  end 
reaction  is  nearly  reached  and  the  amount  of  sugar  solution 
can  no  longer  be  judged  by  the  color  of  the  solution,  a  small 


SUGARS 


117 


portion  of  the  liquid  is  removed  by  means  of  a  filtering-tube, 
placed  in  a  porcelain  crucible  or  on  a  testing  plate,  acidified 
with  dilute  acetic  acid,  and  tested  for  copper  by  solution  of 
potassium  ferrocyanid.  The  sugar  solution  should  be  of  such 
strength  as  will  require  from  15  to  20  c.c.  to  complete  the 
reduction,  and  the  number  of  additions  of  solution  should  be 
as  few  as  possible.  It  is  best  to  verify  the  first  experiment 
by  a  second,  based  on  the  approximation 
which  the  first  gives.  Boiling  for  2  minutes 
should  be  required  for  complete  precipitation 
when  the  full  amount  of  sugar  solution  has 
been  added  in  one  portion.  The  factor  for 
calculation  varies  with  the  minute  details  of 
manipulation  ;  every  operator  must  determine 
the  individual  factor  by  using  a  known  amount 
of  the  form  of  sugar  that  is  to  be  determined 
and  maintaining  conditions  as  uniform  as  pos- 
sible. 

Figure  38  shows  filter-tubes  suitable  for 
obtaining  a  small  quantity  of  the  liquid. 
Wiley's  tube  (A)  is  a  thick-walled  glass  tube 
about  4  cm.  long  on  one  of  which  a  flange 
has  been  made,  over  which  a  piece  of  fine 
linen  is  tied.  Knorr's  tube  (B)  is  much  nar- 
rower, and  has  a  perforated  platinum  disk 
sealed  into  the  lower  end.  The  tube  is  dipped 
into  water  containing  suspended  asbestos,  and 
by  aspiration  a  thin  felt  is  formed  over  the  lower  surface  of 
the  platinum  disk.  The  tube,  thus  prepared,  is  dipped  into 
the  boiling  copper  solution  and  by  aspiration  a  drop  is  drawn 
into  the  tube.  The  Wiley  filter  requires  that  the  liquid  be 
poured  from  the  tube  when  it  is  to  be  tested,  but  with  the 
Knorr  tube  the  asbestos  is  wiped  off,  the  liquid  expelled  through 
the  platinum,  and  the  drop  is  tested  for  copper  as  noted. 


FIG.  38. 


I  1 8  FOOD    ANALYSIS 

Another  method  is  to  remove  a  drop  of  the  boiling  solution 
by  means  of  a  rod  and  place  it  on  a  piece  of  pure  filter-paper. 
The  precipitate  remains  in  the  center  of  the  moistened  spot. 
A  drop  of  potassium  ferrocyanid  solution,  acidulated  with 
acetic  acid,  is  then  placed  near  it ;  as  the  spot  spreads,  a  brown 
stain  will  appear  where  the  liquids  meet,  if  copper  still  be  in 
solution. 

POTASSIUM  COPPER  CYANID  METHOD. 

This  method,  devised  by  Gerrard,  has  been  investigated  by 
A.  H.  Allen,  who  has  pointed  out  the  conditions  necessary  to 
insure  accuracy,  and  regards  it  as  superior  to  other  reduction 
methods.  When  potassium  cyanid  is  added  in  sufficient 
amount  to  copper  sulfate,  a  potassium  copper  cyanid  is 
formed.  This  compound  is  not  decomposed  by  sodium 
hydroxid  or  hydrogen  sulfid.  By  operating  on  a  solution 
containing  an  excess  of  copper  sulfate,  the  reduction  will 
take  place  with  this  excess  only,  and  the  end  of  the  reaction 
is  indicated  by  the  disappearance  of  the  blue  tint  of  the  liquid. 
The  cuprous  oxid  remains  in  solution,  but  as  it  reoxidizes  very 
slowly,  a  brief  exposure  to  air  does  not  interfere  so  much  as 
in  some  other  methods.  The  following  description  is  con- 
densed from  A.  H.  Allen's  "  Chemistry  of  Urine  "  : 

5  c.c.  of  each  of  the  solutions  described  on  page  116  are 
accurately  measured  into  a  porcelain  basin,  40  c.c.  of  water 
added,  the  liquid  heated  to  boiling  and  maintained  so  during 
the  entire  manipulation.  A  solution  of  potassium  cyanid  (5 
grams  in  100  c.c.  of  water)  is  added  gradually  until  only  a 
tinge  of  blue  remains.  An  excess  of  cyanid  must  be  avoided. 
Additional  measures  of  5  c.c.  each  of  the  copper  sulfate  and 
alkaline  tartrate  solutions  are  now  added,  and  when  the  liquid 
begins  to  boil  the  solution  of  sugar  to  be  tested  is  dropped  in 
rapidly.  The  end  reaction  is  sharp  when  pure  solutions  ot 
sugar  are  used.  The  amount  of  reagent  used  is  decolorized 
by  0.05  gram  of  invert-sugar  corresponding  to  0.0475  su- 
crose. 


SUGARS  119 

The  potassium  cyanid  must  be  of  good  quality  ;  the  com- 
mercial article  contains  cyanate,  carbonate,  and  sodium  com- 
pounds. The  solution  of  potassium  copper  cyanid  keeps  for 
some  weeks  ;  hence  if  several  determinations  are  to  be  made, 
a  small  stock  of  solution  may  be  prepared  by  using  ten  times 
the  amounts  directed  above,  adding  300  c.c.  of  water,  decol- 
orizing with  potassium  cyanid  at  the  boiling-point,  and  dilut- 
ing the  liquid  to  500  c.c.  when  cold.  50  c.c.  of  this  liquid 
are  mixed  with  5  c.c.  each  of  the  reagent  solutions  and  the 
titration  proceeded  with. 
SOXH LET'S  EXACT  METHOD. 

An  approximate  determination  of  the  reducing  sugars  in 
the  sample  is  made  by  one  of  the  titration  methods  and  a 
solution  is  prepared  which  contains  nearly,  but  not  more  than, 

1  per  cent,  of  these  sugars.      50  c.c.  of  copper  sulfate  solution 
and  50  c.c.  of  alkaline  tartrate  solution  are  mixed,  added  to  a 
volume  of  the  solution  of  the  sample  estimated  to  be  suffi- 
cient for  the  complete  precipitation  of  the  copper,  boiled  for 

2  minutes,    some  of  the  solution   filtered    rapidly,  and    the 
filtrate  tested  for  copper.     The  process  is  repeated  until  two 
proportions   of  the  solution   of  the   sample   are    determined 
which   differ  by  o.  I  c.c.,  one  giving  complete  reduction  and 
the  other  leaving  a  small  amount  of  copper  in  solution.     The 
mean  of  these  volumes  is  the  amount  of  solution  required  for 
the  volume  of  Fehling's  solution  taken. 

Under  these  conditions,  which  must  be  rigidly  observed,  the 
volume  of  solution  used  will  contain  0.475  gram  of  dextrose 
or  0.494  gram  of  invert-sugar.  As  the  weight  of  the  sample 
which  is  in  this  amount  of  solution  is  known,  the  percentage 
of  either  sugar  may  be  calculated  by  simple  proportion. 
ALLIHN'S  METHOD  FOR  DEXTROSE. 

Copper  sulfate  solution.  34.639  grams  of  pure  crystallized 
copper  sulfate  are  dissolved  in  water  and  made  up  to  500  c.c. 

Alkaline  tartrate  solution.       173  grams   of  pure   potassium 


120  FOOD    ANALYSIS 

sodium  tartrate  and    125   grams  of  potassium  hydroxid  are 
dissolved  in  water  and  made  up  to  500  c.c. 

The  substance  to  be  tested  is  dissolved  in  water  in  such 
proportion  that  the  solution  shall  not  contain  more  than  I  per 
cent,  of  dextrose.  30  c.c.  of  each  of  the  reagent  solutions 
and  60  c.c.  of  water  are  mixed  and  heated  to  boiling,  25  c.c. 
of  the  solution  to  be  examined  are  added,  the  boiling  con- 
tinued for  2  minutes,  and  the  liquid  immediately  filtered  with- 
out dilution,  as  directed  in  connection  with  the  reduction  or 
electrolytic  methods  of  determination  of  copper. 

The  precipitated  cuprous  oxid  is  usually 
converted  into  free  copper  and  weighed  as 
such.  Two  methods  may  be  employed  for  re- 
duction :  by  hydrogen  or  by  electrolysis. 

Reduction  by  Hydrogen. — The  cuprous  oxid 
is  collected  on  an  asbestos  filter.  This  is  ar- 
ranged most  conveniently  in  a  special  filtering 
tube,  which  is  shown  in  figure  38  a.  The 
wider  part  is  about  8  cm.  long  and  1.5  cm.  in 
diameter,  the  narrower  portion  about  5  cm. 
long  and  0.5  cm.  in  caliber.  A  perforated 
platinum  disk  is  sealed  in  just  above  the  point 
FIG!  38  a.  °f  narrowing.  The  asbestos  is  placed  on  this 

disk,  washed  free  from  loose  fibers,  dried  well 
and  the  tube  weighed.  The  filtering  tube  is  attached  to  an 
exhaustion  apparatus  by  passing  narrower  portion  through  the 
cork,  and  a  small  funnel  is  fitted  tightly  in  the  top  of  the  tube. 
The  object  of  this  funnel  is  to  prevent  the  precipitate  -collect- 
ing on  the  upper  part  of  the  tube.  The  lower  end  of  the 
funnel  should  project  several  centimeters  below  the  bottom  of 
the  cork  through  which  it  passes. 

The  filtering  apparatus  must  be  arranged  prior  to  the  pre- 
cipitation, so  that  the  cuprous  oxid  may  be  filtered  without 
delay.  The  precipitate  is  transferred  as  rapidly  as  possible 


SUGARS 


121 


to  the  filter,  well  washed  with  hot  water,  alcohol,  and  ether 
successively,  dried,  and  the  cuprous  oxid  reduced  by  gentle 
heating  in  a  current  of  dry  hydrogen.  When  the  reduction 
is  complete,  the  heat  is  withdrawn,  but  the  flow  of  hydrogen 
is  continued  until  the  tube  is  cold.  It  is  then  detached  and 
weighed.  The  amount  of  sugar  is  determined  by  reference  to 
the  following  table.  Quantities  of  copper  intermediate 
between  those  given  in  the  table  may  be  converted  into  the 
equivalent  in  sugar  by  allowing  for  each  o.ooi  of  copper, 
0.0005  of  dextrose  for  figures  in  the  first  column,  0.00055  for 
figures  in  the  second  column,  and  0.0006  in  the  third  column. 

EQUIVALENTS  FOR  ALLIHN'S  METHOD 


COPPER. 

DEXTROSE. 

COPPER. 

DEXTROSE. 

COPPER. 

DEXTROSE. 

q.oio 

0.0061 

0.170 

0.0869 

0.330 

0.1731 

0.020 

O.OIIO 

0.180 

0.0921 

0.340 

0.1787 

0.030 

0.0160 

0.190 

0.0973 

0.350 

0.1843 

0.040 

0.0209 

0.200 

o.  1026 

0.360 

0.1900 

0.050 

0.0259 

0.210 

0.1079 

0.370 

0.1957 

0.060 

0.0308 

0.220 

0.1132 

0.380 

0.2014 

0.070 

0.0358 

0.230 

0.1185 

0.390 

0.2071 

0.080 

0.0408 

0.240 

0.1239 

0.400 

0.2129 

0.090 

0.0459 

0.250 

0.1292 

0.410 

0.2187 

o.  100 

0.0509 

0.260 

0.1346 

0.420 

0.2245 

o.  no 

0.0560 

0.270 

o.  1400 

0.430 

0.2304 

O.  I  2O 

0.0611 

0.280 

0-1455 

0.440 

0.2363 

0.130 

0.0662 

0.290 

0.1510 

0.450 

0.2422 

0.140 

0.0713 

0.300 

0.1565 

0.460 

0.2481 

o.  150 

0.0765 

0.310 

0.1620 

0.463 

0.2499 

o.  1  60 

0.0817 

0.320 

0.1675 

0.465 

0.2511 

Reduction  of  Copper  by  Electrolysis. — The  filtration  is  per- 
formed in  a  Gooch  crucible  with  an  asbestos-felt  film  and  the 
beaker  in  which  the  precipitation  was  made  is  well  washed 
with  hot  water,  the  washings  being  passed  through  the  filter, 
but  it  is  not  necessary  to  transfer  all  the  precipitate.  When 
the  asbestos  film  is  completely  washed,  it  is  transferred  with 
the  adhering  oxid  to  the  beaker ;  any  oxid  remaining  in  the 


1 1 


122  FOOD    ANALYSIS 

crucible  is  washed  into  the  beaker  by  use  of  2  c.c.  nitric 
acid  (sp.  gr.  1.42),  added  with  a  pipet.  The  crucible  is  rinsed 
with  a  spray  of  water,  the  rinsings  being  collected  in  the 
beaker.  The  liquid  is  heated  until  all  the  copper  is  in  solu- 
tion, filtered,  the  filter  washed  until  the  filtrate  amounts  to  at 
least  100  c.c.,  and  electrolyzed. 


FIG.  39. 

Electrolytic  apparatus  has  been  constructed  in  a  great  variety 
of  forms.  When  the  operation  is  carried  out  frequently,  it  is 
best  to  have  an  electrolytic  table.  A  platinum  basin  holding 
not  less  than  100  c.c.  is  used.  A  cylindrical  form  with  flat 
bottom  is  convenient.  It  should  rest  on  a  bright  copper  plate, 
which  is  connected  with  the  negative  pole  of  the  electrical 


SUGARS  123 

supply.  The  positive  pole  should  be  also  platinum,  either  a 
spiral  wire,  cylinder,  or  flat  foil.  Many  operators  use  a  funnel- 
shaped  perforated  terminal  for  the  negative  pole  ;  as  shown 
in  figure  39.  In  this  case  a  beaker  or  casserole  will  be  a 
suitable  container,  the  positive  terminal  being  placed  within 
the  negative. 

Four  cells  of  a  gravity  battery  will  suffice  for  a  single  de- 
composition, and  will  operate  two,  but  more  slowly.  It  is 
usual  to  arrange  the  apparatus  so  that  the  operation  may  be 
continued  during  the  night.  When  the  electricity  is  taken 
from  the  general  supply  of  the  laboratory,  it  is  usually  neces- 
sary to  interpose  resistance  and  to  have  some  means  of  meas- 
uring the  current-flow.  This  is  sometimes  done  with  a  gas 
evolution  cell  and  incandescent  lamp,  but  an  ammeter  and 
adjustable  rheostat  is  better.  (See  page  66.) 

OPTIC  METHODS. 

The  general  principles  of  polarimetry  have  been  explained 
elsewhere.  For  the  decolorization  and  clarification  of  solu- 
tions, the  following  standard  reagents  are  employed  : 

Lead  subacetate.  Solution  of  lead  acetate  is  boiled  with 
excess  of  lead  monoxid  for  30  minutes,  filtered,  and  brought 
to  a  specific  gravity  of  1.250.  Solid  lead  subacetate  may  be 
used  in  preparing  the  solution. 

Alumina- cream.  A  cold  saturated  solution  of  alum  is 
divided  into  two  unequal  portions  ;  a  slight  excess  of  ammo- 
nium hydroxid  is  added  to  the  larger  portion  and  the  remain- 
der is  added  until  a  faintly  acid  reaction  is  obtained. 

For  sugars  and  molasses  the  normal  weight  for  the 
instrument  is  weighed  out,  washed  into  a  100  c.c.  flask, 
and  water  added  to  make  about  80  c.c.  When  the  material 
has  dissolved  as  far  as  possible,  lead  subacetate  is  added 
until  all  precipitable  matter  has  separated.  (With  mo- 
lasses sufficient  acetic  acid  should  be  added  to  convert  the 
lead  subacetate  into  acetate.)  The  flask  is  filled  to  the  mark, 


124  FOOD    ANALYSIS 

— using,  if  necessary,  a  little  ether  spray  to  break  bubbles, — 
the  solution  filtered  with  a  dry  filter,  the  first  1 5  c.c.  re- 
jected, and  the  reading  taken  on  the  remainder  of  the  filtrate. 
If  the  liquid  is  very  dark,  some  dry  finely-powdered  pure 
bone-black  should  be  used  instead  of  paper  and  the  first  40 
c.c.  of  filtrate  rejected.  All  observations  should  be  made  as 
nearly  as  possible  at  the  temperature  for  which  the  instrument 
is  adjusted.  A  change  of  5°  in  the  interval  between  filling 
the  flask  and  making  the  reading  will  cause,  by  change  of 
volume,  an  error  of  about  o.  I  per  cent,  in  samples  containing 
90  per  cent,  of  sucrose  and  an  error  of  about  0.5  per  cent,  in 
samples  containing  50  per  cent,  of  sucrose. 

With  juices  or  other  dilute  materials,  weighing  may  be 
omitted,  and  100  c.c.  of  the  sample  placed  in  a  flask  marked 
IOO  c.c.  and  1 10  c.c.,  the  clarifying  reagents  added,  the  flask 
filled  to  the  110  c.c.  mark,  filtered  as  above,' and  a  reading 
taken.  The  following  formula  may  be  employed  for  calcu- 
lating results  : 

Percentage  of  sucrose  =  l'1  X  readi"g  on  suEar  scale  x  normal  weight  for  instrument 

100  X  specific  gravity  of  sample 

A.   O.  A.   C.   INVERSION  METHOD. 

A  clear  solution  is  made  according  to  one  of  the  methods 
given  above.  50  c.c.  of  the  filtrate  are  placed  in  a  flask 
marked  at  50  and  55  c.c.,  5  c.c.  of  pure  fuming  hydrochloric 
acid  added,  and  the  liquids  well  mixed.  The  flask  is  heated 
in  water  until  the  thermometer,  with  the  bulb  as  near  the 
center  of  the  solution  as  possible,  marks  68°.  About  15 
minutes  should  be  required  for  this  heating.  The  flask 'is  then 
removed,  cooled  quickly  to  room  temperature,  and  polarized, 
noting  the  temperature.  If  the  sample  originally  contained 
invert-sugar,  the  second  polarization  should  be  made  at  ap- 
proximately the  same  temperature  as  the  first.  The  calcula- 
tion of  the  amount  of  sucrose  is  made  by  adding  the  two 
readings  if  they  are  on  opposite  sides  of  the  zero,  or  subtract- 


SUGARS  I  2  5 

ing  them  if  they  are  on  the  same  side,  and  dividing  the  result 
in  either  case  by  143  less  half  the  observation  temperature  in 
centigrade  degrees.  The  rule,  therefore,  may  be  expressed  by 
the  following  formula  : 

g  _     a±6 


a  being  the  first  and  b  the  second  reading,  which  are  added 
when  of  opposite  signs  and  subtracted  when  of  like  signs  ; 
that  is,  the  algebraic  difference  is  taken,  in  either  case. 

With  dark-colored  materials  it  will  often  be  advantageous 
to  add  an  excess  of  alumina  cream.  Alumina  cream  alone 
will  often  suffice  for  clarification. 

When  lead  subacetate  is  used  with  liquids  containing  levu- 
lose,  it  is  necessary  to  render  the  filtrate  acid  in  order  to  break 
up  a  compound  which  the  levulose  forms  with  the  lead. 

GERMAN  OFFICIAL    METHOD. 

26.048  grams  of  the  sample  are  dissolved  in  a  sugar  flask  and 
the  solution  made  up  to  100  c.c.  ;  50  c.c.  of  this  solution  are 
transferred  by  means  of  a  pipet  to  a  flask  graduated  at  50  and 
55  c.c.,  enough  lead  subacetate  solution  added  for  clarification, 
the  volume  made  up  to  the  55  c.c.  mark,  and  the  liquid  thor- 
oughly shaken  and  filtered.  The  filtrate  is  then  polarized,  the 
reading  being  corrected  for  the  extra  5  c.c.  The  liquid  ad- 
hering to  the  pipet  is  washed  into  the  100  c.c.  flask  containing 
the  remaining  50  c.c.  (13.024  grams),  5  c.c.  of  concentrated 
hydrochloric  acid  (38  per  cent.,  specific  gravity  i.iSSat  15°) 
added,  and  the  flask  placed  in  a  water-bath  the  temperature  of 
which  is  70°.  The  contents  of  the  flask  should  reach  a  tem- 
perature of  67°-7O°  in  two  or  three  minutes,  when  the  tem- 
perature should  be  maintained  within  this  limit  for  exactly  five 
minutes,  keeping  the  temperature  as  nearly  69°  as  possible. 
(See  international  agreement,  page  29,  as  to  standard  weight 
of  sugar.) 


126  FOOD    ANALYSIS 

SUCROSE 

Under  the  term  sucrose  all  forms  of  table  sugar  are  in- 
cluded. These  are,  principally,  the  sugar-cane,  SaccJiarum 
officinarum  L.  ;  beet,  Beta  vulgaris  L.  ;  sorghum,  Sorghum 
saccharatum  Persoon ;  sugar  maple,  Acer  saccharinum  L. 
In  the  crude  state  there  is  a  noticeable  difference  in  these 
varieties,  but  so  far  as  is  known,  the  sucrose  is  identical  in  all 
cases. 

Adulterations  are  rarely  encountered.  The  addition  of 
glucose,  especially  to  the  lower  grades,  formerly  extensively 
practised,  now  rarely  occurs.  The  difference  in  the  grades 
depends  largely  upon  the  extent  to  which  the  molasses  and 
mineral  matter  have  been  removed.  Maple  sugar  is  sold  in 
the  crude  condition  and  is  often  adulterated. 

The  usual  examination  of  commercial  sugar  is  determina- 
tion of  the  amount  of  water,  ash,  sucrose,  and  reducing 
sugar.  Water  and  ash  are  determined  as  on  page  48.  In 
the  best  grades  of  sugar  these  together  will  often  not  amount 
to  more  than  o.  I  per  cent.  In  the  lower  grades  ash  may  be  3 
percent.,  and  water  between  loand  15  percent.  The  higher 
proportions  of  ash  are  found  in  beet-sugar.  The  estimation 
of  sucrose  is  most  conveniently  made  by  the  polarimeter. 
The  direct  reading  is  usually  sufficient,  but  the  result  may  be 
checked  by  inversion,  and  reading  at  ordinary  temperature 
and  at  86°.  The  best  grades  will  give  a  direct  reading  closely 
approximating  100  per  cent.  In  some  cases  the  direct  read- 
ing will  slightly  exceed  100,  due  to  a  small  proportion  of 
raffinose.  The  lower  grades  of  sugar  contain  some  invert- 
sugar  and  the  proportion  of  sucrose  may  be  even  below  80 
per  cent.  Maple  sugar  usually  contains  about  85  per  cent,  of 
sucrose. 

COLORING-MATTERS. — Granulated  and  loaf  sugars  often  con- 
tain ultramarine  blue,  added  to  improve  color.  It  may  be 
separated  by  dissolving  a  considerable  quantity  of  the  sample 


SUGARS  1 27 

iii  water,  allowing  the  coloring-matter  to  subside,  and  washing 
it  with  water  several  times  by  decantation.  Ultramarine  blue 
is  decomposed  by  hydrochloric  acid,  the  color  discharged, 
and  hydrogen  sulfid  liberated. 

Tin  chlorid  is  sometimes  employed  in  order  to  give  sugar 
a  bright,  lasting,  yellow  color.  The  color  appears  to  be  the 
result  of  action  on  the  sucrose.  As  a  rule,  the  finished 
product  contains  but  traces  of  tin,  the  greater  portion  being 
removed  with  the  molasses.  The  so-called  Demerara  sugar 
is  prepared  in  this  way.  Demerara  sugar  is  frequently 
imitated  by  the  addition  of  artificial  coloring,  usually  to  beet- 
sugar.  To  separate  such  added  coloring-matter  Cassel  rec- 
ommends the  following  method  : 

About  i  oo  grams  of  the  sample  are  shaken  with  alcohol  of 
90  per  cent.  This  will  often  remove  the  color  in  a  single 
washing.  In  some  cases  it  is  advisable  to  use  alcohol  of  75 
or  80  per  cent.  The  solution  is  filtered  from  the  sugar, 
evaporated  to  dryness,  the  color  again  taken  up  with  alcohol, 
and  a  skein  of  silk  or  wool  (preferably  slightly  mordanted 
with  aluminum  acetate)  treated  with  the  solution,  warmed  for 
some  time,  and  subsequently  well  washed  with  water.  The 
skein  will  be  dyed  of  a  more  or  less  yellow  color  in  the  pres- 
ence of  artificial  dye.  A  sample  containing  only  such  color- 
ing-matter as  is  natural  to  sugar,  even  by  repeated  washing 
with  alcohol  of  90  per  cent.,  does  not  leave  absolutely  color- 
less crystals,  and  does  not  give  a  solution  capable  of  perma- 
nently dyeing  silk  or  wool.  It  is  probable  that  the  wool  test 
described  on  page  77  might  be  successfully  applied  to  a 
solution  in  water.  See  also  Crampton  and  Simon's  test  for 
caramel,  page  130. 

The  occasional  occurrence  of  saccharin  as  a  substitute  for 
sugar  in  confections,  fruit  juices,  jams,  and  similar  articles  must 
not  be  overlooked.  The  detection  of  saccharin  is  given  in 
the  section  on  "  Preservatives."  The  possibility  of  commercial 


128  FOOD    ANALYSIS 

glucose  and  invert-sugar  containing  arsenic  and  lead  derived 
from  the  sulfuric  acid  must  also  be  borne  in  mind. 

MOLASSES    AND    SIRUP 

Molasses  is  the  uncrystallizable  sirup  produced  in  the 
manufacture  of  sugar.  It  properly  differs  from  treacle  in  that 
it  comes  from  sugar  in  the  process  of  making,  while  treacle  is 
obtained  in  the  process  of  refining,  but  the  two  terms  are  usu- 
ally employed  synonymously.  Treacle,  often  called  refiner's 
molasses,  may  contain  35  per  cent,  or  more  of  sucrose,  which 
is  prevented  from  crystallizing  by  the  associated  substances. 
Ordinary  table-molasses  is  made  from  cane,  sorghum,  or 
maple.  Molasses  from  raw  cane-sugar  contains  considerable 
invert-sugar,  from  which  beet-root  molasses  is  comparatively 
free.  The  latter,  however,  contains  raffinose  and  a  great 
variety  of  other  bodies  ;  the  proportion  of  salts  being  some- 
times 1 5  per  cent.  These  impurities  render  it  unfit  for  table 
use.  Beet-sugar  partially  or  wholly  refined  is  free  from  these 
ingredients  and  may  be  used  in  the  preparation  of  table  sirups. 

Maple  sirup  is  molasses  from  the  maple.  Much  so-called 
maple  sirup  or  "  mapleine  "  is  made  by  addition  of  extract  of 
hickory-bark  to  sucrose  or  glucose  sirup.  This  use  of  ex- 
tract of  hickory-bark  has  been  patented  in  the  United  States. 

Molasses  and  maple  sirup  are  often  adulterated  by  the  addi- 
tion of  glucose  sirup.  The  product  is  usually  sold  as  molasses, 
but  is  sometimes  designated  "  mixed  goods  "  or  "  table  sirup." 
Glucose  sirup  produces  a  good  body  and  light  color,  and 
many  samples  consist  almost  entirely  of  this  material,  flavored 
by  the  addition  of  a  small  proportion  of  the  lowest  grades  of 
refuse  molasses. 

The  addition  of  glucose  to  molasses  is  readily  detected  by 
means  of  the  polariscope.  The  normal  or  one-half  normal 
quantity  for  the  instrument  is  dissolved  in  water,  clarified,  and 
made  up  to  100  c.c.,  as  described  on  page  123,  and  the  read- 


SUGARS 

ing  taken.  A  portion  of  this  solution  is  inverted,  as  described 
on  page  124,  and  two  readings  taken,  one  at  or  near  the 
same  temperature  as  the  direct  reading,  and  a  second  at  86° 
(see  page  125).  Pure  molasses  generally  gives  on  direct 
reading  at  a  temperature  of  20°  a  deviation  corresponding  to 
40  or  50  on  the  cane-sugar  scale.  After  inversion,  the 
reading  at  the  same  temperature  will  be  — 10  or  — 20,  and  at 
a  temperature  of  86°  will  be  zero  or  near  it.  Sirups  made 
by  the  solution  of  sucrose  in  water  will  usually  give  a  rather 
higher  direct  reading,  but  after  inversion  the  results  will  be 
the  same  as  with  molasses.  In  the  presence  of  any  consid- 
erable quantity  of  glucose  the  direct  reading  is  nearly  always 
above  60  and  may  rise  to  1 20  or  more.  After  inversion,  the 
sample  remains  strongly  dextrorotatory  even  at  86°. 

Dark  molasses  is  often  bleached.  Bone-black  is  sometimes 
used,  but  ozone,  hydrogen  dioxicl,  sulfurous  acid,  sulfites, 
and  sulfuric  acid  have  been  employed.  One  method  consists 
in  the  addition  of  zinc  dust  and  sodium  sulfite,  the  zinc  being 
subsequently  removed  by  the  addition  of  oxalic  acid.  The 
bleached  molasses  is  liable,  therefore,  to  contain  either  zinc 
or  oxalic  acid. 

As  noted  above,  some  samples  of  sugar  are  prepared  by 
the  use  of  stannous  chlorid  ;  the  latter  may  pass  into  the  mo- 
lasses in  such  proportion  as  to  be  dangerous.  Copper  is  occa- 
sionally present,  derived  from  the  apparatus  of  the  refinery. 
For  the  detection  of  metallic  impurities  in  molasses,  not  less 
than  50  grams  should  be  ashed  and  examined  as  described 
on  page  69. 

CARAMEL  is  a  dark  brown  mass,  soluble  in  water  and 
weak  alcoholic  liquids,  obtained  by  heating  sucrose  to  about 
200°.  It  is  largely  used  as  a  coloring-matter  in  foods  and 
beverages.  It  is  now  occasionally  adulterated  or  imitated  by 
artificial  coal-tar  colors.  Arata's  wool  test  will  serve  in  many 
cases  to  detect  these.  Caramel  as  a  coloring  agent  is  most 

12 


130  FOOD    ANALYSIS 

easily  recognized  by  a  method  due  to  Crampton  and  Simons  : 
The  liquid  is  well  shaken  with  a  small  quantity  of  fuller's 
earth  and  filtered.  Coloring  matters  from  charred  or  un- 
charred  wood  are  not  removed,  but  if  caramel  be  present  the 
filtrate  will  be  noticeably  paler  than  the  original  liquid.  See 
also  under  "  Alcoholic  Beverages." 

GLUCOSE 

Commercial  glucose  consists  principally  of  dextrose  with 
considerable  maltose  and  gallisin  and  some  dextrin.  In  trade 
the  term  "  glucose  "  is  restricted  to  the  sirup ;  the  solid  is 
called  "  grape-sugar."  Inferior  qualities  of  glucose  may  con- 
tain sulfurous  or  sulfuric  acid,  calcium  sulfate,  arsenic,  and 
lead.  A  large  number  of  cases  of  poisoning  caused  by  beer 
made  from  arsenical  glucose  and  invert-sugar  occurred  in 
England  in  1900. 

The  following  are  analyses  of  commercial  glucoses,  presum- 
ably all  from  maize-starch.1  6  Nos.  i  and  2  are  by  Moritz  and 
Morris  ;  3  and  4  by  L.  Stern.  In  Stern's  analyses  some  fig- 
ure has  been  determined  by  difference,  probably  that  given  as 
"  unfermentable  bodies,"  in  which  the  gallisin  and  nitrogen- 
ous matters  are  included.  The  nature  and  effects  of  these 
accessory  bodies  are  uncertain,  but  the  figures  show  that 
commercial  glucoses  will  differ  in  reducing  power  and  optic 
activity. 

No.  i.  No.  2.  No.  3.  No.  4. 

Dextrose, 50.58  47-71  70.0  67.4 

Maltose,      H-I9  12.29  5-1  II-° 

Dextrin,       . 1.76  2.98 

Gallisin, 15-59  lS-9° 

Nitrogenous  matters,     .......  1.18  o.8l 

Unfermentable  bodies,      14.08  4.3 

Ash, 1.44  1.39  0.2  1.6 

Water, 16.49  20.77  9-9  I5-7 

101.23        101.85       100.0          100.0 

The  examination  of  glucose  samples  may  be  conducted  as 
follows  : 


SUGARS  I  3  I 

Arsenic  may  be  detected  by  Reinsch's  test;  lead  by  the 
routine  method  given  on  page  71.  The  amount  of  free  acid 
is  determined  by  titration  of  a  known  weight  with  standard 
alkali,  using  phenolphthalein  as  indicator.  Sulfurous  acid 
may  be  detected  by  adding  some  of  the  samples  to  dilute 
hydrochloric  acid,  with  a  few  fragments  of  zinc  in  a  test-tube, 
and  covering  the  mouth  of  the  tube  with  a  piece  of  filter- 
paper  containing  some  lead  acetate.  A  spot  of  lead  sulfid 
indicates  reducible  sulfur  compounds.  Calcium  sulphate  or 
other  mineral  matter  may  be  determined  by  the  weight  and 
composition  of  the  ash. 

LACTOSE 

Commercial  lactose  is  usually  obtained  from  the  whey  of 
cows'  milk.  Inferior  qualities  contain  notable  amounts  of 
nitrogenous  matter,  mineral  substances,  bacteria,  and  spores 
of  fungi.  Pure  lactose  is  a  white  crystalline  powder,  not 
very  soluble  in  water  and  feebly  sweet.  When  crystallized  by 
evaporation  at  low  temperature,  it  retains  one  molecule  of 
water,  but  this  is  easily  removed.  The  freshly  made  solution 
in  water  has  a  dextrorotatory  power  much  greater  than 
normal  ;  upon  standing  for  24  hours,  or  immediately  upon 
boiling,  it  acquires  its  normal  rotatory  action.  This  phe- 
nomenon, known  as  "  birotation,"  must  not  be  overlooked  in 
examining  samples  of  lactose  or  concentrated  milk-products. 
Lactose  has  high  reducing  power,  especially  upon  alkaline 
copper  solutions.  Under  the  influence  of  some  common 
organisms  it  is  rapidly  converted  into  lactic  acid  ;  by  special 
methods  it  may  be  converted  into  ethyl  alcohol. 

For  qualitative  tests  for  lactose  see  page  1 14.  Quantitative 
determinations  are  made  either  with  a  polarimeter  or  an 
alkaline  copper  solution.  The  details  of  these  methods  are 
given  in  connection  with  the  analyses  of  milk.  The  examina- 
tion of  commercial  samples  should  be  directed  to  the  deter- 
mination of  the  amount  of  nitrogen,  ash,  lead,  copper,  and 


132  FOOD    ANALYSIS 

zinc.     The  sample  should  not  be  acid,  nor  contain  any  appre- 
ciable amount  of  matter  insoluble  in  water. 


MAPLE  SIRUP  AND.  MAPLE  SUGAR 

These  are  substantially  sucrose  with  minute  amounts  of 
special  flavors.  Sucrose  from  other  sources  may,  therefore, 
be  added  in  large  amounts  without  being  detected  by  any 
direct  method.  It  is  claimed,  however,  by  some  analysts  that 
the  amount  of  ash  of  a  sample  may  be  a  guide,  since  a  good 
sucrose  contains  but  a  small  amount  of  mineral  matter.  Suf- 
ficient data  are  not  yet  at  hand  to  decide  upon  this  point. 
Adulteration  with  glucose  solution  maybe  detected  by  polari- 
metric  examination  before  and  after  inversion,  as  directed  in 
connection  with  examination  of  sucrose.  Pure  maple  sirup 
is  converted  into  invert-sugar  and  shows  a  decided  change 
from  positive  to  negative,  while  glucose  is  not  affected.  The 
following  results,  given  by  A.  W.  Ogden,1  7  will  illustrate  this 
method  : 


Maple     sirups 
f  r  e  e     from 
glucose  : 

Maple  sugars  : 

Maple     sirups 
containing 
glucose  : 

c  i 

POLARIME 

Direct. 

:TER  READING. 
After  Inversion. 
—  22.2 
-21.9 
-I7.6 
—  2O.  O 

—28.8 
-28.3 
—29-3 
18.9 

45-6 
37-7 
61.2 

PERCENTAGE 
SUCROSE. 

56.0 
60.6 

57-7 
62.4 

85-9 
87.6 
88.5 

\1  ' 

59-6 
56  7 

u 

61.7 

f  I 

.    84  i 

(1: 

88.0 
88.4 

- 

1  •? 

80.0 

.     .     .    IOO  O 

.     06  4 

J 

4,    - 

Q7-4 

HONEY 

Honey  is  the  nectar  of  flowers  and  other  saccharine  exuda- 
tions of  plants  collected  and  stored  by  the  hive  bee,  Apis 
mellifica.  Similar  material  is  produced  by  other  species  of 
bees  and  by  some  wasps  and  ants. 


HONEY  133 

Honey  consists  principally  of  dextrose  and  levulose  with 
small  proportions  of  mineral  and  flavoring  matters  and  often 
formic  acid.  In  some  cases  siruill  amounts  of  sucrose  and 
mannitose  and  a  considerable  proportion  of  carbohydrates  of 
the  dextrin  class  are  present.  Microscopic  examination  will 
usually  show  pollen,  portions  of  insects'  wings,  and  spores  of 
fungi.  Crystallized  dextrose  is  occasionally  present. 

The  color  of  honey  varies  from  light  amber-yellow  to 
brownish-black,  according  to  the  source  and  time  and  man- 
ner of  storage.  White  clover  honey  is  nearly  colorless. 
Strained  honey  is  that  freed  from  comb. 

The  proportion  of  water  ranges  within  the  limits  of  12  and 
22  per  cent,  the  ash  is  rarely  over  0.3  per  cent.  The  re- 
ducing bodies  calculated  as  dextrose  usually  amount  to  from 
60  to  75  per  cent.  If  sucrose  be  present  in  but  small  amount 
in  the  nectar  of  the  flowers,  it  may  be  entirely  inverted  in  the 
bee  or  after  deposition  in  the  hive,  the  resulting  honey  being 
quite  free.  The  maximum  proportion  which  may  be  present  in 
pure  honey  is  as  yet  unknown.  Some  authorities  have  pro- 
posed 5  per  cent.,  others  are  disposed  to  allow  a  much  higher 
proportion,  but  it  is  probable  that  the  lower  limit  will  rarely 
be  exceeded  in  pure  samples. 

Honey  contains  no  true  dextrin,  but  many  samples  yield, 
with  strong  alcohol,  precipitates  of  carbohydrate  intermediate 
between  starch  and  sugar,  the  proportion  being  as  high  as  40 
per  cent,  or  more  in  the  case  of  honey  of  coniferous  origin. 

Honey  is  mostly  levorotatory.  Using  the  normal  sugar- 
weight  and  measured  on  the  sucrose  scale  at  a  temperature  of 
20°  it  will  show  a  deviation  of — 2  to  — 14,  but  the  following 
table  shows  some  dextrorotatory  results  from  samples  of 
undoubted  purity.  They  were  probably  derived,  in  part, 
from  the  black  cherry,  and  also  from  the  honey-dew  of  a 
neighboring  pine  forest.  Other  observers  have  noted  dextro- 
rotation  in  honey  of  coniferous  origin. 


34 


FOOD    ANALYSIS 


POLARIZATION. 

REDUCING 

TEMPERA- 
TURE, °C. 

SUCROSE. 

CARBO- 
HYDRATE CAL- 
CULATED AS 
DEXTROSE. 

WATER. 

ASH. 

Direct. 

After 
Inversion. 

8.2 

2.8 

29.0 

5-0 

64.52 

17.00 

0.12 

7.2 

3-3 

29.0 

3-1 

66.45 

18-33 

O.  IO 

5-i 

2.4 

30.0 

2.1 

63.42 

18.65 

0.19 

7-3 

2.6 

29-5 

3-6 

58.42 

16.72 

0.2O 

0.6 

—  2.2 

29.0 

2.2 

64.  10 

19.60 

0.25 

ADULTERATIONS. — Bees  are  often  fed  with  cane-sugar,  which 
is  partially  inverted  by  them,  but  the  product  is  inferior  in 
flavor  to  true  honey.  Ogden  gives  the  following  results  of 
polarimetric  examination  of  honey  in  the  comb  obtained  in 
this  way : 

Direct,  i80.5-     Temperature,  25.2°. 

After  inversion,     — 9.0.     Temperature,  24°. 

The  common  adulterants  of  strained  honey  are  invert-sugar 
and  glucose  sirup.  It  is  usually  impossible  to  detect  with 
certainty  the  addition  of  invert-sugar.  An  ash  higher  than 
0.3  per  cent.,  containing  a  notable  quantity  of  calcium  sul- 
fate,  may  point  to  invert-sugar  or  to  glucose  sirup.  Samples 
are  frequently  encountered  which  give  a  direct  polarimetric 
reading  of  — 14  to  — 20  on  the  cane-sugar  scale,  and,  after 
inversion,  slightly  higher  figures  ;  these  in  most  cases  probably 
contain  added  invert-sugar,  but  it  is  not  possible  at  present  to 
establish  this  point. 

The  direct  addition  of  sucrose  to  honey  is  not  usual,  but 
has  been  practised  in  some  cases.  Its  presence  in  considerable 
quantity  will  be  indicated  by  the  high  right-handed  rotation, 
decidedly  reduced  on  inversion.  A  sample  of  so-called 
"hoarhound  honey"  examined  in  the  chemical  laboratory  of 
the  United  States  Department  of  Agriculture  was  found  to 
consist  mainly  of  a  solution  of  sucrose  with  some  alcohol. 
The  analytic  results  were  as  follows  : 


HONEY 


135 


POLARIZATION. 

TEMPERA- 
TURE, °C. 

SUCROSE. 

REDUCING 
BODIES  CAL- 
CULATED AS 
DEXTROSE. 

WATER, 
PER 
CENT. 

ASH, 
PER 
CENT. 

Direct. 

After 
Inversion. 

78.90 

2.40 

24.6 

58.I 

7.92 

23.12 

0.03 

A  common  method  of  adulteration  consists  in  pouring 
glucose  sirup  over  honeycomb  from  which  the  honey  has 
been  drained,  and  allowing  the  mixture  to  stand  until  it  has 
acquired  a  honey  flavor.  Such  samples  give  a  high  positive 
polarimetric  reading,  but  little  affected  by  inversion  with  acid. 
The  following  are  some  results  of  examination  of  honey  con- 
taining glucose  : 


WATER. 

• 

ASH. 

POLARIZATION. 

REDt 

BODIES 
AS  DE> 

CING 

CALC. 

.TROSE. 

SUCROSE. 

SOLIDS 

NOT 

DETER- 
MINED. 

Direct. 

oc. 

After 
inv. 

•c. 

Before 
inv. 

After 
inv. 

By 
Polar. 

Reduc. 

16.93 

22.45 
i5-4i 
1907 

O.2I 

0.31 

£3 

74-50 
74.00 
89.50 
24-65 
26.38 

2t-5 
24-5 
21-5 
23-0 
25-5 

60.18 
57-40 
51-99 
40.0 
57.60 
65-23 

61.33 
59-85 

57  oo 
64-35 
64.85 

3-99 

16.50 
5-84 

0.00 

1.09 
2-33 

16.15 
6.43 

0.00 

15-42 
25-39 

0.50 
19-53 
15-52 

73-80 
67.50 
16.90 
23-50 

24.0 

21.6 
22.6 
25.0 

Dextrin  is  a  constant  constituent  of  commercial  glucose 
sir-up,  and  the  attempt  has  been  made  to  detect  the  latter  by 
the  formation  of  a  precipitate  when  the  sample  is  diluted  with 
alcohol.  It  has  been  shown,  however,  that  many  samples  of 
honey  contain  a  considerable  material  precipitable  by  ethyl 
alcohol,  amounting  in  some  instances  to  50  per  cent.  Accord- 
ing to  Beckmann,  better  results  may  be  obtained  by  the  use 
of  methyl  alcohol.  Pure  honey,  both  the  ordinary  form  and 
the  dextrorotatory  variety,  that  might  be  regarded  as  adul- 
terated with  glucose,  was  found  to  yield,  when  largely  diluted 


136  FOOD    ANALYSIS 

with  methyl  alcohol,  only  a  slight  flocculent  precipitate,  which 
did  not  adhere  to  the  walls  of  the  vessel.  Glucose  sirup 
yielded  a  precipitate  of  dextrin  amounting  to  about  31  per 
cent.,  which  produced  with  a  solution  of  iodin  in  potassium 
iodid  the  red  characteristic  of  erythrodextrin.  The  reaction 
is  also  obtained  by  direct  addition  of  the  iodin  solution  to 
honey  containing  glucose  sirup.  The  quantitative  determina- 
tion is  made  by  diluting  8  grams  of  the  sample  with  8  c.c.  of 
water  and  diluting  the  mixture  to  100  c.c.  with  methyl 
alcohol.  The  precipitate  is  filtered  off,  washed  with  methyl 
alcohol,  dissolved  in  water,  and  the  solution  evaporated  on  the 
water-bath  with  repeated  addition  of  methyl  alcohol  until  quite 
dry.  Adulteration  with  solid  glucose  (so-called  grape-sugar) 
cannot  be  detected  by  this  method,  since  in  the  preparation 
of  this  the  conversion  is  carried  beyond  the  point  at  which 
dextrin  is  formed.  Methyl  alcohol  produces  only  a  slight 
turbidity. 

Beckmann  has  also  proposed  the  following  test  for  solid 
glucose  and  glucose  sirup  :  5  c.c.  of  the  honey  solution  (20 
grams  in  100  c.c.  of  water)  are  mixed  with  3  c.c.  of  a  2  per 
cent,  solution  of  barium  hydroxid,  17  c.c.  of  methyl  alcohol 
added,  and  the  mixture  shaken.  Pure  honey  remains  clear, 
but  in  the  presence  of  dextrin,  glucose,  or  glucose  sirup  a 
considerable  precipitate  is  formed.  The  test  was  applied 
quantitatively  by  increasing  the  amount  taken  to  50  grams, 
the  methyl  alcohol  added  rapidly  to  avoid  deposition  on  the 
glass,  the  liquid  well  shaken  once,  the  precipitate  collected  on 
a  tared  asbestos  filter,  washed  with  methyl  alcohol  and  ether, 
and  dried  at  55°-6o°.  Excessive  shaking  was  avoided  in 
order  to  prevent  the  action  of  air  on  precipitate.  It  was  found 
that  the  quicker  the  working,  the  more  accurate  the  results. 
In  some  cases  it  was  found  necessary  to  determine  the  sulfates 
and  phosphates  and  to  correct  the  results  accordingly.  The 
mean  results  in  test  analyses,  calculated  to  I  gram  of  the 


HONEY  137 

material  taken,  were:  Dextrin,  0.916  gram;  glucose  sirup, 
0.455  gram;  solid  glucose,  0.158  gram.  Admixture  of 
dextrorotatory  conifer  honey  to  the  extent  of  90  per  cent, 
was  not  found  to  increase  the  amount  of  precipitate,  but,  on 
the  contrary,  to  diminish  it  slightly. 

The  following  are  results  obtained  on  samples  of  natural 
honey  rich  in  dextrinous  bodies.  Sp.  is  the  specific  rotatory 
power  for  yellow  light : 

Apple  honey,     .    .    .  Sp.  =  — 12.2.     Precipitate  by  ethyl  alcohol  23.7  per  cent. 
Barium  precipitate  5  c.c.  10  per  cent,  solution  gave  0.0044  gram. 
"  "          5  c.c.  20  per  cent.        "  "      0.0072     " 

Umbellifer  honey,     .  Sp.  =-.    — 4.6.     Precipitate  by  ethyl  alcohol  29.1  per  cent. 
Barium  precipitate  5  c.c.  10  per  cent,  solution  gave  0.0148  gram. 
"  "          5  c.c.  20  per  cent.        "  "     0.023       " 

Conifer  honey,  .    .    .  Sp.  =      16.9.     Precipitate  by  ethyl  alcohol  41.9  per  cent. 

Barium  precipitate  5  c.c.  10  per  cent,  solution  gave  0.0132  gram. 

"  "  5  c.c.  20  per  cent.       "  *'     0.0248  gram. 

It  appears  from  these  data  that  even  under  unfavorable  cir- 
cumstances it  is  possible  to  recognize  the  addition  of  from  5 
to  10  per  cent,  of  ordinary  dextrin,  10  to  20  per  cent,  of 
glucose  sirup,  and  30  to  40  per  cent,  of  solid  glucose  to 
conifer  containing  as  much  as  40  per  cent,  of  natural  dex- 
trinous matter.  With  ordinary  samples,  such  as  the  apple 
honey  just  noted,  adulteration  would  be  much  more  easily 
detected. 

Molasses  is  said  to  have  been  added  to  honey,  but  its 
use  is  infrequent.  The  ash  of  molasses  is  high  and  con- 
tains considerable  chlorids.  Beckmann  suggests  its  detection 
by  the  production  of  a  precipitate  on  addition  of  a  solution  of 
lead  subacetate  in  methyl  alcohol,  the  formation  of  which  is 
attributed  to  the  presence  of  raffinose.  5  grams  of  the  solu- 
tion are  mixed  with  22.5  c.c.  of  methyl  alcohol  and  5  c.c.  of 
a  solution  of  the  honey  (which  should  not  contain  more  than 
25  per  cent.)  are  added.  If  the  honey  be  pure,  the  solution 
will  remain  clear,  but  in  the  presence  of  molasses  a  precipitate 


138  FOOD    ANALYSIS 

will  be  formed.  The  amount  of  precipitate  varies  according 
to  the  particular  sample  of  molasses  present,  but  Beckmann 
claims  that  it  will  usually  be  possible  to  detect  as  low  as  10 
per  cent. 

Konig  and  Karsch18  have  proposed  the  following  method 
for  detection  of  glucose  :  40  grams  of  the  sample  are  made  up 
to  40  c.c.  with  water,  well  mixed,  20  c.c.  placed  in  a  250  c.c. 
flask,  and  absolute  alcohol  added,  by  very  small  portions  at  a 
time,  with  constant  shaking,  until  the  flask  is  filled  to  the 
mark.  The  mixture  is  allowed  to  stand  for  several  days  with 
occasional  shaking.  The  solution  is  again  shaken  well  and 
quickly  filtered.  100  c.c.  of  the  filtrate  are  evaporated  to 
remove  alcohol,  but  not  to  dryness,  the  residue  made  up  to  20 
c.c.  by  addition  of  lead  subacetate  and  water,  and  the  solution 
examined  in  the  polarimeter. 

The  precipitate  produced  by  alcohol  is  washed  several 
times  with  90  per  cent,  alcohol  and  then  dissolved  off  the 
filter  with  water,  evaporated  on  the  water-bath,  dried  in  the 
water-oven,  and  weighed. 

The  following  are  some  of  the  results  obtained  : 

PERCENTAGE  OF  REDUC- 

POLARIMETRIC    READING.  ING   CARBOHYDRATES 

Before  Treatment     After  Treatment         PRECIPITATED  BY 
with  Alcohol.  with  Alcohol.  ALCOHOL. 

Pure  honey,      — 6.4  — 8.5  3.2 

—12.4  13.4  1.7 

— 16.7  17.0  .    .    . 

—ii. 7  n-7  3-3 

— 9.2  13.2  ... 

—7-7  9-9                          9-7 

—9-9  12-5 

—7-5  6-2                        34-0 
Honey    containing    75    per 

cent,  glucose, 25.5  2.4                           20.6 

CANDIES  AND  CONFECTIONS 

These  terms  include  many  articles,  including  complex 
mixtures,  the  composition  of  which  is  secret.  The  main 
ingredient  is  usually  sucrose,  but  invert-sugar,  dextrose, 


CANDIES    AND    CONFECTIONS  139 

starch,  mucilaginous  substances,  gelatin,  colors,  and  flavors 
are  largely  employed.  Among  the  objectionable  ingredients 
are  paraffin,  clay,  calcium  sulfate,  mineral  colors,  fusel  oil, 
and  metal  foil.  Preservatives  are  usually  unnecessary.  The 
use  of  mineral  colors  has  declined  much  of  late  years,  owing 
to  the  cheapness  and  superior  brilliancy  of  artificial  organic 
dyes,  but  some  of  the  chocolate  confections  contain  consider- 
able amounts  of  brown  ferric  hydroxid. 

The  plain  candies,  such  as  rock  candy,  molasses  candy,  and 
candy  toys  are  usually  only  crystallized  or  melted  sucrose 
with  flavors  and  colors.  Actual  experiment  by  manufacturing 
confectioners  has  furnished  the  following  data  for  proportion 
of  color : 

One  part  of  auramin  will  color  30,000  parts  of  melted  sucrose 
to  the  deepest  yellow  required.  One  part  of  eosin  or  fluores- 
cein  will  give  the  average  tint  to  28,000  parts  of  "cream 
goods"  (such  as  used  in  high-class  "mixtures")  or  21,000 
parts  of  clear  and  hard  candies,  or  12,000  to  24,000  parts  of 
some  other  types.  These  figures  are  for  "solid"  coloring — 
that  is,  the  whole  mass  is  dyed  ;  when  merely  surface-coloring 
•is  done,  the  quantity  needed  is  about  I  part  to  50,000. 

The  ash  of  candies  and  confections  is  generally  below  one 
per  cent.  The  flavors  are  often  artificial.  A  brand  called 
"  Rock  and  Rye  Drops"  is  .often  flavored  with  fusel  oil. 

The  colors  employed  are  numerous  and  constantly  chang- 
ing. At  present  various  eosins  (e.  g.y  rhodamin  B,  rose 
bengale,  erythrosin)  are  much  used  for  red,  fluorescein  and 
auramin  for  yellow,  malachite  green  and  sulfonated  allies  for 
green.  Natural  chlorophyl  is  sometimes  used.  Bismarck 
brown  is  apt  to  be  employed  in  chocolate  colors,  although 
disapproved  by  the  National  Confectioners'  Association.  Its 
list  will  furnish  suggestions  as  to  the  color  likely  to  be 
present  in  any  sample. 

Analytic   Methods. — The    examination  of    candies    will  be 


I4O  FOOD    ANALYSIS 

usually  limited  to  identification  of  the  coloring-matters  and 
detection  of  starch,  clay,  calcium  sulfate,  paraffin,  and  poison- 
ous metals.  Determination  of  sucrose,  invert-sugar,  dextrose, 
and  gum  are  difficult  and  of  no  practical  interest. 

A  weighed  portion  of  the  sample  is  stirred  in  cold  water 
until  all  soluble  matter  is  taken  up,  the  liquid  is  filtered  in  a 
Gooch  crucible,  the  residue  washed  with  cold  water,  trans- 
ferred to  the  crucible,  dried  at  a  low  heat,  weighed,  burnt  off, 
and  again  weighed.  The  figures  for  insoluble  residue  and 
ash  will  be  obtained.  The  aqueous  solution  will  usually 
contain  the  coloring  and  some  of  the  flavoring  material ;  the 
former  may  often  be  identified  by  the  tests  given  on  pages  80 
to  82.  Many  flavoring  agents  may  be  recognized  by  odor. 
Starch  may  be  detected  by  iodin.  Any  notable  amount  of 
gelatin  or  albumin  will  be  indicated  by  the  Kjeldahl  method. 
Clay,  calcium  sulfate,  and  iron  oxid  will  be  found  in  the  ash. 


FATS  AND  OILS 

The  methods  for  determining  melting  and  solidifying  points 
and  specific  gravity  of  fats  and  oils  have  been  fully  described 
in  the  introductory  part.  Some  comparative  data  are  given 
in  this  section,  together  with  methods  applied  almost  exclu- 
sively to  this  class  of  food-products. 

Specific  gravity  determined  at  temperatures  other  than 
15.5°  may  be  reduced  to  this  by  a  correction  of  0.00064  for 
each  degree.  This  figure  is  derived  from  results  obtained  by 
A.  H.  Allen.  The  specific  gravity  of  fats  and  oils  changes 
by  time.  The  following  table,  due  to  Thomson  and  Ballen- 
tyne,  shows  this  fact ;  the  figures  are  for  |^° : 

FRESH.  ONE  MONTH.  THREE  MONTHS.  Six  MONTHS. 

Olive,       0.9168  0.9187                   0.9208                   0.9246 

Cottonseed,     ....  0.9225  0.9237                 0.9261                 0.9320 

Arachis, 0.9209  0.9213                 0.9233                 0.9267 

Rape, .  0.9168  0.9183                 0.9188                 0.9207 


FATS    AND    OILS  14! 

Color-tests. — Many  color-tests  for  oils  and  fats  have  been 
proposed.  The  reactions  are  in  many  cases  dependent  on 
accessory  materials  and  may  fail  when  the  sample  has  been  pro- 
duced under  unusual  conditions  or  subjected  to  special  treat- 
ment. Thus,  cottonseed  oil  by  heating  loses  susceptibility 
to  several  color-tests,  while  lard  derived  from  animals  fed 
liberally  on  cottonseed  products  will  give  distinctly  the  cotton- 
seed oil  reactions.  Special  color-tests  applicable  to  particular 
oils  or  fats  will  be  described  in  connection  with  these.  The 
following  general  reactions  are  much  used  : 

SULFURIC  ACID  TEST. — A  drop  or  two  of  strong  sulfuric 
acid  is  placed  in  the  center  of  about  20  drops  of  oil,  allowed 
to  rest  a  few  moments,  the  color  change  noted,  the  mixture 
stirred,  and  the  effect  again  noted.  The  charring  action  which 
often  obscures  the  reaction  may  be  avoided  by  dissolving  a 
drop  of  the  oil  in  20  drops  of  carbon  disulfid  and  agitating 
this  with  the  sulfuric  acid. 

NITRIC  ACID  TEST. — O.  Bach's  method  is  to  agitate  5  c.c. 
of  the  sample  with  5  c.c.  of  nitric  acid,  sp.  gr.  1.30.  The 
color  reaction  is  noted,  the  mixture  immersed  in  boiling  water 
for  5  minutes,  and  the  condition  again  noted.  As  the  reaction 
on  heating  may  be  violent,  care  must  be  taken  that  no  injury 
be  done. 

Massie's  method  is  to  agitate  10  grams  with  5  c.c.  of  nitric 
acid,  sp.  gr.  1.40,  and  note  the  color  at  the  end  of  one  hour. 

J.  Lewkowitsch  states  that  an  acid  of  specific  gravity  1.375 
gives  often  the  best  results.  In  some  cases  the  mixture 
should  stand  24  hours  before  the  final  observation  is  made. 

Mixtures  of  strong  sulfuric  acid  and  strong  nitric  acid  have 
been  used,  but  the  results  are  interesting  specially  in  the  case 
of  certain  fish  oils. 

The  following  data,  compiled  by  A.  H.  Allen,19  will  illus- 
trate the  value  of  these  color-tests  : 


142 


FOOD    ANALYSIS 


OLIVE. 

COTTON- 
SEED. 

SESAME. 

ARACHIS. 

RAPE. 

SULFURIC  ACID.  — 

Before  stirring,  . 
After  stirring,    . 

Yellow- 
green 
or  brown. 
Brown  or 
green. 

Red-br-.wn. 

Dark     red- 
brown. 

Yellow     to 
orange. 

Green       or 
brown. 

Yellow 
with 
red  rings. 
Brown. 

NITRIC  ACID.  — 

Bach's  test  : 

After  agitation. 
After  heating, 
After  1  2  hours' 

Pale- 
green. 
Orange- 
yellow. 

Yellow- 
brown. 
Red-brown. 

White. 

Brown- 
yellow. 

Pale  rose 

Brown- 
yellow. 

Pale  rose. 

Orange- 
yellow. 

standing,    . 
Massie's  test,     . 

Solid. 
Yellow- 

Buttery. 
Orange-red 

Liquid. 
Yellow- 

Solid. 
Pale  red. 

Solid 
Orange. 

Time  for  solidifica- 

green. 

orange. 

tion  (minutes),  . 

60 

105 

105 

200 

lodin  Number. — This,  also  called  iodin  value,  is  the  per- 
centage of  iodin  absorbed  under  specified  conditions.  Baron 
Hiibl  discovered  that  a  solution  of  iodin  and  mercuric  chlorid 
was  more  uniform  in  action  than  iodin  alone,  and  this  solution, 
commonly  known  as  Hiibl's  reagent,  is  usually  employed. 
The  following  reagents  are  used  in  the  process  : 

Iodin  solution.  25  grams  of  iodin  are  dissolved  in  500  c.c. 
of  95  per  cent,  alcohol. 

Mercuric  chlorid  solution.  25  grams  of  mercuric  chlorid 
solution  are  dissolved  in  500  c.c.  of  95  per  cent,  alcohol  and 
the  solution  filtered,  if  necessary. 

Starch  solution.  A  solution  of  5  grams  of  starch  in  200 
c.c.  of  water. 

Potassium  io did  solution.      15  grams  in  100  c.c.  of  water. 

Potassium  dichromate  solution.  3.874  grams  of  pure  potas- 
sium dichromate  in  1000  c.c.  of  water. 

For  use,  equal  parts  of  the  iodin  and  mercuric  chlorid 
solutions  are  mixed  and  allowed  to  stand  at  least  12  hours. 


FATS    AND    OILS  143 

\ 

The  strength  of  the  thiosulfate  solution  is  determined  as 
follows  :  20  c.c.  of  potassium  dichromate  solution,  10  c.c.  of 
potassium  iodid  solution,  and  5  c.c.  of  strong  hydrochloric  acid 
are  mixed  in  a  glass-stoppered  flask,  and  the  solution  of  sodium 
thiosulfate  is  allowed  to  flow  in  from  a  buret«until  the  yellow 
color  of  the  mixture  has  almost  disappeared.  A  few  drops 
of  starch  solution  are  then  put  in  and  the  addition  of  the 
thiosulfate  continued  until  the  blue  color  just  appears.  The 
number  of  cubic  centimeters  of  thiosulfate  solution  used, 
multiplied  by  5,  is  equivalent  to  I  gram  of  iodin. 

Not  more  than  I  gram  of  fat  is  weighed  in  a  glass-stoppered 
flask  holding  about  300  c.c.,  and  10  c.c.  of  chloroform  are 
added.  After  complete  solution  30  c.c.  of  the  iodin  solution 
are  added  and  the  flask  is  placed  in  the  dark  for  three  hours, 
with  occasional  shaking.  100  c.c.  of  water  and  20  c.c.  of 
potassium  iodid  solution  are  added  to  the  contents  of  the 
flask.  Any  iodin  which  may  be  noticed  upon  the  stopper  of 
the  flask  should  be  washed  back  into  the  flask  with  the 
potassium  iodid  solution.  The  excess  of  iodin  is  now  titrated 
with  the  sodium  thiosulfate  solution,  which  is  run  in  gradually, 
with  constant  shaking,  until  the  yellow  color  of  the  solution 
has  almost  disappeared.  A  few  drops  of  starch-paste  are 
added,  and  the  titration  continued  until  the  blue  color  has 
entirely  disappeared.  Toward  the  end  of  the  reaction  the 
flask  should  be  closed  and  violently  shaken,  so  that  iodin 
remaining  in  the  chloroform  may  be  taken  up  by  the  potassium 
iodid  solution.  A  sufficient  quantity  of  sodium  thiosulfate 
solution  should  be  added  to  prevent  a  reappearance  of  any 
blue  color  in  the  flask  for  five  minutes. 

At  the  time  of  adding  the  iodin  solution  to  the  fats,  two 
flasks  of  the  same  size  as  those  used  for  the  determination 
should  be  employed  for  conducting  the  operation  without  fat. 
In  every  other  respect  the  performance  of  the  blank  experi- 


144  FOOD    ANALYSIS 

ments  should  be  just  as  described.  These  blank  experiments 
must  be  made  each  time  the  iodin  solution  is  used. 

IODIN  NUMBER  OF  LIQUID  ACIDS. — This  determination  is 
sometimes  of  value  for  detection  of  admixture  of  vegetable 
oils  with  animal. oils.  The  separation  of  the  oleic  and  other 
liquid  fatty  acids  is  best  made  by  the  method  of  J.  Muter  and 
L.  De  Koningh,  as  follows  : 

3  grams  of  the  fat  are  mixed  with  50  c.c.  of  alcohol  and  a 
fragment  of  potassium  hydroxid  in  a  flask  furnished  with  a 
long  tube.  The  mixture  is  boiled  until  saponification  is  com- 
plete, when  a  drop  of  phenolphthalein  solution  is  added  and 
acetic  acid  until  the  solution  is  slightly  acid.  Alcoholic 
solution  of  potassium  hydroxid  is  added  drop  by  drop  until  a 
faint  permanent  pink  tint  is  obtained,  when  the  liquid  is  poured 
slowly,  with  constant  stirring,  into  a  beaker  containing  a  boil- 
ing solution  of  3  grams  of  neutral  lead  acetate  in  200  c.c.  of 
water.  The  solution  is  rapidly  cooled  and  stirred  at  the  same 
time,  and,  when  cold,  the  clear  liquid  is  poured  off.  The 
precipitate  is  well  washed  with  boiling  water  by  decantation, 
transferred  to  a  stoppered  bottle,  mixed  with  1 20  c.c.  of  ether, 
and  allowed  to  remain  12  hours.  Wallenstein  and  Finck  use 
a  Drechsel  gas-washing  flask  having  the  tube  shortened  about 
two-thirds,  to  contain  the  ethereal  solution,  and  pass  a  current 
of  hydrogen  through  it  for  about  a  minute.  In  the  case  of 
white  fats  the  liquid  is  said  to  remain  colorless  at  the  end  of 
12  hours,  but  if  free  access  of  air  is  permitted,  a  dark-yellow 
solution  is  produced  by  oxidation.  Lead  oleate,  hypogeate, 
linolate,  or  ricinolate  will  be  dissolved  by  the  ether, 'leaving 
lead  laurate,  myristate,  palmitate,  stearate,  and  arachidate 
undissolved.  Lead  erucate  is  sparingly  soluble  in  cold  ether, 
but  readily  in  hot.  The  contents  of  the  bottle  are  filtered 
through  a  covered  filter  into  a  Muter  separating-tube  (Fig. 
40),  40  c.c.  of  dilute  hydrochloric  acid  (1:4)  added,  and  the 
tube  shaken  until  the  clearing  of  the  ethereal  solution  shows 


FATS    AND    OILS 


that  the  decomposition  of  the  lead  soaps  is  complete.  The 
aqueous  liquid,  containing  lead  chlorid  and  excess  of  hydro- 
chloric acid,  is  run  off  through  the  bottom  tap,  water  added, 
and  agitated  with  the  ether  and  the  process  of  washing  by 
agitation  repeated  until  the  removal  of  the  acid  is  complete. 
Water  is  then  added  to  the  zero  mark  and  sufficient  ether  to 
bring  the  ether  to  a  definite  volume  (e.  g,,  200  c.c.).  An 
aliquot  portion  of  this  (e.  g.,  50  c.c.)  is  then 
removed  through  the  side  tap  and  the  residue 
weighed  after  evaporation  of  the  ether  in  a 
current  of  carbon  dioxid.  Another  aliquot 
portion  of  the  ethereal  solution  should  be  dis- 
tilled to  a  small  bulk  (avoiding  complete  evap- 
oration), alcohol  added,  and  the  solution 
titrated  with  decinormal  sodium  hydroxid 
and  phenolphthalein  or  methyl-orange,  from 
which  the  fatty  acids  may  be  calculated  from 
the  result,  or  their  mean  combining  weight 
deduced  therefrom.  A  third  aliquot  part  of 
the  ethereal  solution  should  be  evaporated  at 
about  60°  in  a  flask  traversed  by  a  rapid  stream 
of  dry  carbon  dioxid.  When  every  trace  of 
ether  is  removed,  50  c.c.  of  the  iodin-mercur- 
ic  chlorid  solution  (p.  142)  should  be  added, 
the  stopper  inserted,  and  the  liquid  kept  in 
absolute  darkness  for  12  hours,  after  which 
an  excess  of  potassium  iodid  solution  is  added 
and  250  c.c.  of  water,  and  the  excess  of  iodin  ascertained  with 
thiosulfate  solution  in  the  usual  way.  From  the  result  the 
iodin  number  is  calculated. 

Volatile  Acids. — This  method  was  first  suggested  by  Otto 

Hehner  and  A.  Angell,  but  was  systematized  by  E.  Reichert, 

and  hence  is  generally  called  the  Reichert  process.     In  this 

form  it  is  carried  out  by  saponifying  2.5   grams  of  the  fat, 

13 


FIG.  40. 


146  FOOD    ANALYSIS 

adding  excess  of  sulfuric  acid,  distilling  a  definite  portion  of 
the  liquid,  and  titrating  the  distillate  with  N  alkali.  The  num- 
ber of  cubic  centimeters  of  this  solution  required  to  overcome 
the  acidity  of  the  distillate  is  called  the  Reichert  number.  E. 
Meissl  suggested  the  use  of  5  grams,  and  the  number  so 
obtained  is  called  the  Reichert-Meissl  number.  Alcoholic 
solution  of  potassium  hydroxid  was  originally  used  for  sap- 
onification,  but  most  chemists  now  use  the  solution  devised 
by  Leffmann  and  Beam,  namely,  sodium  hydroxid  in  glycerol. 
The  reagents  and  operation  are  as  follows  : 

Glycerol-soda. — 100  grams  of  pure  sodium  hydroxid  are 
dissolved  in  100  c.c.  of  distilled  water  and  allowed  to  stand 
until  clear.  20  c.c.  of  this  solution  are  mixed  with  180  c.c. 
of  pure  concentrated  glycerol.  The  mixture  can  be  conveni- 
ently kept  in  a  capped  bottle  holding  a  10  c.c.  pipet,  with  a 
wide  outlet. 

Sulfuric  Acid. — 20  c.c.  of  pure  concentrated  sulfuric  acid, 
made  up  with  distilled  water  to  100  c.c. 

Sodium  Hydroxid. — An  approximately  decinormal,  accu- 
rately standardized,  solution  of  sodium  hydroxid. 

Indicator. — An  alcoholic  solution  of  phenolphthalein  or 
aqueous  solution  of  methyl-orange. 

A  300  c.c.  flask  is  washed  thoroughly,  rinsed  with  alco- 
hol and  then  with  ether,  and  thoroughly  dried  by  heat- 
ing in  the  water-oven.  After  cooling,  it  is  allowed  to 
stand  for  about  15  minutes  and  weighed.  A  pipet,  gradu- 
ated to  5.75  c.c.,  is  heated  to  about  60°  and  filled  to  the 
mark  with  the  well-mixed  fat,  which  is  then  run  into  the 
flask.  After  standing  for  about  15  minutes  the  flask  and  con- 
tents are  weighed.  20  c.c.  of  the  glycerol-soda  are  added 
and  the  flask  heated  over  the  Bunsen  burner.  The  mixture 
may  foam  somewhat ;  this  may  be  controlled,  and  the  opera- 
tion hastened  by  shaking  the  flask.  When  all  the  water  has 
been  driven  off,  the  liquid  will  cease  to  boil,  and  if  the  heat 


FATS    AND    OILS 


147 


and  agitation  be  continued  for  a  few  moments,  complete  sap- 
onification  will  be  effected,  the  mass  becoming  clear.  The 
whole  operation,  exclusive  of  weighing  the  fat,  requires  about 
five  minutes.  The  flask  is  withdrawn  from  the  heat  and  the 
soap  dissolved  in  135  c.c.  of  water.  The  first  portions  of 
water  should  be  added  drop  by  drop,  and  the  flask  shaken 
between  each  addition  in  order  to  avoid  foaming.  When  the 
soap  is  dissolved,  5  c.c.  of  the  dilute  sulfuric  acid  are  added, 


FIG.  41. 


a  piece  of  pumice  dropped  in,  and  the  liquid  distilled  until 
110  c.c.  have  been  collected.  The  condensing  tube  should 
be  of  glass,  and  the  distillation  conducted  at  such  a  rate  that 
the  above  amount  of  distillate  is  collected  in  30  minutes. 

The  distillate  is  usually  clear  ;  if  not,  it  should  be  thor- 
oughly mixed,  filtered  through  a  dry  filter,  and  100  c.c.  of 
the  filtrate  taken.  A  little  of  the  indicator  is  added  to  the 
distillate,  and  the  standard  alkali  run  in  from  a  buret  until 
neutralization  is  attained.  If  only  100  c.c.  of  the  distillate 


148  FOOD    ANALYSIS 

have  been  used  for  the  titration,  the  number  of  cubic  centi- 
meters of  alkali  should  be  increased  by  one-tenth. 

The  distilling  apparatus  shown  in  figure  43  is  that  recom- 
mended by  the  A.  O.  A.  C.  (and  since  adopted  in  Great 
Britain),  and  the  directions  for  preparing  the  flask  are  also 
from  the  same  source,  but  when  it  is  intended  merely  to  dis- 
tinguish butter  from  oleomargarin,  it  will  be  sufficient  to 
measure  into  a  flask  3  or  6  c.c.  of  the  clear  fat,  and  operate 
upon  this  directly  in  an  ordinary  distilling  apparatus. 

A  blank  experiment  should  be  made  to  determine  the 
amount  of  standard  alkali  required  by  the  materials  employed. 
With  a  good  quality  of  glycerol,  this  will  not  exceed  0.5  c.c. 

Most  fats  give  distillates  containing  but  little  acid. 

Saponification  Value. — Koettstorfer  Number. — This  is 
the  number  of  milligrams  of  potassium  hydroxid  required  for 
the  saponification  of  I  gram  of  fat.  Its  use  was  suggested 
by  M.  Berthelot,  and  it  was  applied  to  the  examination  of 
butter  by  J.  Koettstorfer.  If  the  saponification  value  be 
divided  by  10,  the  result  will  be  the  percentage  of  alkali 
required  for  saponification.  The  reagents  and  process  are  as 
follows  : 

Alcoholic  potassium  hydroxid.  40  grams  of  good  potassium 
hydroxid  are  dissolved  in  sufficient  95  per  cent,  alcohol  to 
make  1000  c.c.  of  alcohol.  The  solution  should  be  clear  and 
not  darker  than  light  yellow.  Alcohol  that  becomes  brown 
is  unfit  for  use. 

Purified  methyl  alcohol  may  be  substituted  for  ethyl 
alcohol.  Sodium  hydroxid  may  be  substituted  for  potassium 
hydroxid.  The  saponification  value  of  sodium  hydroxid  may 
be  converted  into  the  standard  number  by  multiplying  by 
1.4025. 

Half-normal  hydrochloric  acid  accurately  standardized. 

Phenolphthalein  solution. 

The  process  is  as  follows  :  About  1.5  grams  of  the  sample 


FATS    AND    OILS 


149 


are  accurately  weighed  into  a  small  flask,  25  c.c.  of  the 
alcoholic  alkali  added,  and  the  mass  saponified.  The  same 
amount  of  the  alkaline  solution  must  be  used  in  all  compara- 
tive experiments,  and  it  must  be  accurately  measured.  The 
flask  is  heated  under  an  inverted  condenser  or,  more  simply, 
with  a  tube  about  50  cm.  long  and  0.5  cm.  caliber  passing 
through  the  cork.  The  flask  is  heated  on  the  water-bath  for 
30  minutes,  being  occasionally  given  a  rotatory  motion.  The 
alcohol  should  not  boil  actively.  A  drop  of  the  indicator 
solution  is  added,  the  liquid  allowed 
to  cool  somewhat,  the  flask  being 
closed,  and  then  titrated  with  the 
standard  acid.  A  blank  test  should 
be  made,  which  will  eliminate  some 
of  the  errors  of  experiment.  The 
number  of  cubic  centimeters  used 
for  titration  of  the  saponified  mass, 
subtracted  from  the  number  used 
in  the  blank  experiment,  will  give 
the  acid  corresponding  to  the  alkali 
which  has  been  neutralized  by  the 
fat.  From  this,  the  amount  of  alkali 
can  be  determined  and  calculated  by 
simple  proportion  to  I  gram  of  fat. 

Flasks  of  the  same  kind  of  glass  should  be  used  in  com- 
parative experiments,  as  some  of  the  cheaper  forms  of  glass 
are  notably  affected  by  alkali.  A  special  form  of  saponifica- 
tion  flask  and  method  of  heating  used  by  the  A.  O.  A.  C.  are 
shown  in  figure  42.  The  flask  is  arranged  so  that  the  cork 
can  be  tied  down. 

A.  H.  Allen  suggested  the  use  of  the  figure  representing 
the  grams  of  fat  saponified  by  1000  c.c.  of  normal  alkali. 
This  would  render  the  method  independent  of  the  alkali 
employed,  but  the  suggestion  has  not  been  generally  approved. 


FIG.  42. 


I  5O  FOOD    ANALYSIS 

The  datum  was  called  by  Allen  saponification  equivalent.  It 
may  be  obtained  in  any  case  by  dividing  56100  by  the  saponi- 
fication number.  Similarly,  the  saponification  number  may 
be  obtained  by  dividing  56100  by  the  saponification  equiva- 
lent. 

Acid  Value. — This  is  the  amount  of  free  fatty  acids  pres- 
ent in  the  sample.  The  reagents  and  process  are  as  follows  : 

Sodium  hydroxid  solution.  Decinormal  solution  of  sodium 
hydroxid. 

Neutral  alcolwl.  Alcohol  (95  per  cent.)  carefully  neutral- 
ized by  addition  of  a  drop  or  two  of  phenolphthalein  solution, 
and  running  in  the  alkali  solution  until  the  color-change 
occurs.  10  grams  of  the  sample  are  placed  in  a  bottle  pro- 
vided with  a  glass  stopper,  about  50  c.c.  of  the  neutral  alco- 
hol and  I  c.c.  of  the  indicator  added,  and  the  mass  heated  to 
boiling  by  immersing  the  bottle  in  hot  water.  The  bottle  is 
then  stoppered  and  well  agitated  and  the  liquid  titrated  with 
standard  alkali,  the  bottle  being  vigorously  shaken  after  each 
addition  until  a  faint  pink  coloration  persists  for  a  minute  or 
two.  On  long  standing  the  alkali  acts  upon  the  fat  itself. 
I  c.c.  of  decinormal  alkali  is  equivalent  to  0.0256  gram  of 
palmitic  acid,  0.0284  gram  of  stearic  acid,  or  0.0282  gram  of 
oleic  acid.  As  the  acid  present  may  not  be  known,  it  is 
usual  to  express  the  result  as  the  milligrams  of  potassium 
hydroxid  required  to  neutralize  I  gram  of  fat.  This  is  called 
the  acid  number.  When  sodium  hydroxid  is  used  for  titra- 
tion,  the  acid  number  may  be  calculated  by  multiplying  the 
quantity  of  sodium  hydroxid  required  for  I  gram  of  sample 
by  1.4. 

Solubility  in  Acetic  Acid. — Valenta's  Test. — Fats  and 
oils  are  arranged  by  Valenta  into  three  classes,  according  to 
their  solubility  in  acetic  acid.  Equal  volumes  of  the  oil  and 
acid  are  placed  in  a  test-tube,  thoroughly  mixed,  and,  if  no 
solution  takes  place,  warmed. 


FATS    AND    OILS  !$! 

Class  i. — Completely  soluble  at  ordinary  temperature  : 
Olive  kernel  oil ;  castor  oil. 

Class  2. — Completely  soluble  or  nearly  so  at  temperatures 
ranging  from  23°  up  to  the  boiling-point  of  glacial  acetic 
acid  :  Palm  oil ;  coconut  oil ;  olive  oil ;  cacao-butter  ;  sesame 
oil ;  cottonseed  oil  ;  arachis  oil  ;  beef  tallow  ;  butter,  etc. 

Class  3. — Not  completely  dissolved  even  at  the  boiling- 
point  of  glacial  acetic  acid  :  Oils  obtained  from  the  seeds  of 
the  Crucifera ;  rape-seed  oil ;  mustard-seed  oil ;  hedge-mus- 
tard oil. 

For  the  practical  application  of  the  test  the  method  of  W. 
A.  Chattaway,  T.  M.  Pearmain,  and  C.  G.  Moor  is  satisfac- 
tory : 

2.75  grams  of  the  sample  are  weighed  in  a  short,  rather 
thick  tube  with  a  well-fitting  stopper,  3  c.c.  of  acetic  acid 
(99.5  per  cent.)  are  added,  the  tube  closed,  placed  in  a  beaker 
of  warm  water,  and  the  heat  increased  until,  after  well  shaking 
the  tube,  the  contents  become  quite  clear.  The  source  of 
heat  is  then  removed,  and  the  test-tube  so  placed  that  it  is  in 
the  center  of  the  beaker  of  heated  water,  and,  by  means  of  a 
thermometer  attached  to  the  tube  by  a  rubber  band,  the 
whole  is  allowed  to  rest  until  the  change  from  brilliancy  to 
turbidity  takes  place.  The  change  is  very  definite,  and  can 
be  repeated  as  often  as  is  wished,  with  a  maximum  error  of 
about  0.25°. 

Thermal  Reaction  with  Sulfuric  Acid. — Maumen6's 
Test — Maumene  found  that  on  mixing  sulfuric  acid  with 
drying  oils  a  higher  temperature  is  produced  than  with  non- 
drying  oils.  With  the  same  sample  the  temperature  will 
depend  upon  the  acid.  The  strength  of  acid  employed 
should  be  determined  by  titration,  since  the  specific  gravity 
of  the  acid  of  96  per  cent,  and  of  99  per  cent,  is  practically 
identical.  L.  Archbutt  recommends  the  following  method  of 
operating  :  50  grams  of  the  sample,  weighed  closely,  are 


152  FOOD    ANALYSIS 

placed  in  a  beaker  "of  200  c.c.  capacity,  and,  together  with 
the  bottle  of  acid,  placed  in  a  vessel  of  water  until  both  have 
acquired  the  temperature  of  the  water,  the  thermometer  hav- 
ing been  placed  in  the  oil.  The  beaker  is  removed  from  the 
water,  wiped  outside,  and  placed  in  a  nest  of  cardboard  having 
hollow  sides  stuffed  with  cotton.  (A  large  beaker,  lined  with 
cotton,  may  also  be  used.)  The  temperature  having  been 
noted,  10  c.c.  of  acid  are  rapidly  withdrawn  from  the  bottle, 
which  is  immediately  closed,  the  acid  is  allowed  to  flow  into 
the  oil  while  it  is  being  stirred  with  the  thermometer,  and  the 
stirring  is  continued  until  no  further  rise  of  temperature  is 
observed.  The  stirring  must  be  so  managed  as  to  effect  as 
perfect  admixture  of  the  oil  and  acid  as  possible,  thereby  in- 
suring an  even  development  of  heat  throughout  the  mixture. 

The  best  results  are  obtained  with  an  acid  about  97  per 
cent.  It  is  desirable  to  keep  on  hand  a  stock  of  oil  of  known 
purity,  and  to  test  some  of  this  with  each  set  of  samples 
examined. 

Specific  Temperature  Reaction. — The  discrepancies  ob- 
served in  Maumene's  method  may  be  largely  eliminated  by 
that  devised  by  R.  T.  Thomson  and  H.  Ballentyne,  which  is 
to  compare  the  rise  of  temperature  with  oil  and  with  an  equal 
volume  of  water  under  similar  conditions.  The  number  ob- 
tained by  dividing  the  oil  figure  by  the  water  figure  is  multi- 
plied by  100  to  eliminate  decimals,  and  the  datum  so  obtained 
is  called  the  specific  temperature  reaction. 

Bromin  Thermal  Value. — O.  Hehner  and  C.  A.  Mitchell 
ascertained  that  the  heat  evolved  in  the  reaction  of  bromin 
with  unsaturated  fatty  bodies  furnishes  more  definite  data  than 
does  sulfuric  acid.  As  the  action  of  bromin  upon  some  oils 
is  violent,  it  is  moderated  by  the  use  of  a  diluent  such  as 
chloroform  or  glacial  acetic  acid.  The  latter  has  the  advan- 
tage, owing  to  its  high  boiling-point,  of  allowing  a  wider 
range  of  temperature.  The  procedure  is  as  follows  :  The 


FATS    AND    OILS  153 

bromin,  oil,  and  diluent  are  all  brought  to  the  same  tempera- 
ture. I  gram  of  the  oil  is  dissolved  in  10  c.c.  of  chloroform 
in  a  vacuum-jacketed  test-tube.  Exactly  I  c.c.  of  bromin 
(measured  by  means  of  a  pipet,  connected  at  the  upper  end 
with  a  narrow  tube  filled  with  caustic  lime,  and  having  an  as- 
bestos plug  at  each  end)  is  added  and  the  rise  of  temperature 
determined  by  a  thermometer  graduated  into  fifths.  Acids 
are  dissolved  in  glacial  acetic  acid  instead  of  chloroform. 

A  definite  relation  exists  between  the  iodin  number  and  the 
heat  produced  by  bromin.  In  Hehner  and  Mitchell's  experi- 
ments it  was  found  that  if  the  rise  of  temperature  in  degrees 
was  multiplied  by  5.5,  a  close  approximation  to  the  iodin 
number  was  always  obtained,  except  with  rape  and  linseed 
oils,  but  each  observer  must  ascertain  the  factor  applying  to 
particular  cases. 

H.  W.  Wiley  has  made  this  method  more  accurate  and 
more  easy  of  application.  A  solution  of  bromin  in  four 
parts  by  volume  of  chloroform  or  carbon  tetrachlorid  is  em- 
ployed. This  is  to  be  made  up  in  quantity  sufficient  for  one 
day's  use,  and  kept  in  the  dark.  Dissolving  the  sample  in 
similar  solvents  is  an  additional  convenience.  10  grams  of 
the  sample,  in  sufficient  chloroform  or  carbon  tetrachlorid  to 
make  50  c.c.  of  solution,  will  suffice  for  nine  determinations. 
At  least  four  determinations  should  be  made.  The  apparatus 
is  shown  in  figure  43.  The  tube  for  holding  the  reagent  and 
thermometer  is  about  40  cm.  in  length,  and  1.5  cm.  internal 
diameter.  It  is  conveniently  held  in  a  drying  jar,  being  fitted 
air-tight  by  a  rubber  stopper.  Air  is  withdrawn  from  the 
jacketing  jar  through  the  side  tubulure.  The  bromin  solu- 
tion is  contained  in  a  stout-walled  Erlenmeyer  flask  with  a 
side  tubulure  provided  with  a  rubber  bulb.  Through  the 
stopper  passes  a  pipet,  and  the  flask  may  be  rendered  air- 
tight by  gentle  pressure  on  the  stopper.  The  thermometer 
should  be  graduated  to  0.2°  and  be  read  to  a  tenth  by  a  lens. 
14 


154 


FOOD    ANALYSIS 


The   operation  should   be  conducted  in  a  room  at  uniform 
temperature. 

The  solutions  and  apparatus  are  allowed  to  stand  until  all 


FIG.  43. 


reach  a  uniform  temperature.  5  c.c.  of  the  solution  of  the 
sample  are  placed  in  the  inner  tube  by  means  of  the  pipet, 
without  allowing  any  of  the  solution  to  run  down  the  walls 


FATS    AND    OILS  155 

of  the  tube,  the  thermometer  is  inserted,  and  the  bromin  so- 
lution is  forced  up  into  the  pipet  by  compressing  the  rubber 
bulb  until  the  liquid  has  passed  the  mark  on  the  stem.  The 
top  of  the  pipet  is  closed  by  the  finger,  the  stopper  of  the 
flask  loosened,  and  the  liquid  allowed  to  run  out  until  it 
reaches  the  mark,  when  it  is  transferred  to  the  mixing  tube 
and  allowed  to  flow  directly  into  the  solution  of  fat,  but  it  is  now 
not  necessary  to  prevent  the  liquid  running  down  the  side  of 
the  tube.  The  empty  pipet  is  returned  to  the  flask  and  the 
thermometer  is  observed  at  once  by  means  of  a  lens  since  the 
bromination  is  practically  instantaneous,  the  mercury  reaching 
its  maximum  height  in  about  a  minute  after  the  pipet  is  with- 
drawn. When  the  mercury  begins  to  fall,  air  is  admitted  to 
the  jacketing  space,  the  mixing  tube  is  withdrawn,  its  con- 
tents emptied,  and  the  tube  held  inverted  until  the  residual 
bromin  vapor  escapes.  The  tube  may  be  cleaned  by  wiping 
it  with  a  long  test-tube  cleaner  or  may  be  used  again  without 
cleaning,  after  standing  inverted  for  half  an  hour.  Traces  of 
brominated  oil  which  may  remain  upon  the  side  of  the  tube 
do  not  interfere  unless  they  obscure  the  thermometer.  By 
the  above  manipulation  the  thermometer  soon  returns  to  the 
room  temperature,  and  a  second  determination  may  be  made 
in  half  an  hour. 

As  noted  by  Hehner  and  Mitchell,  each  analytic  system 
must  be  separately  standardized  and  the  factor  for  calculating 
the  iodin  absorption  determined.  It  is  important  not  to  stir 
or  churn  the  mixture  of  oil  and  bromin  further  than  is  pro- 
duced by  the  running  in  of  the  solution  itself.  Carbon  tetra- 
chlorid  is  the  preferable  solvent,  but  the  rise  of  temperature 
is  slightly  higher  with  chloroform. 

A.  H.  Gill  and  I.  Hatch  have  proposed  to  facilitate  the 
comparison  of  tests  made  with  different  apparatus  by  employ- 
ing a  standardizing  material,  and  recommend  sublimed  cam- 
phor for  this  purpose.  7. 5  grams  of  the  camphor  are  dis- 


156  FOOD    ANALYSIS 

solved  in  carbon  tetrachlorid,  the  solution  made  up  to  25  c.c., 
and  portions  of  5  c.c.  each  brominated.  The  temperature 
increase  obtained  with  various  oils  is  divided  by  the  rise  ob- 
served with  camphor,  giving  a  specific  temperature  increase, 
analogous  to  that  suggested  by  Thomson  &  Ballantyne  (see 
p.  152).  By  dividing  the  iodin  value  of  an  oil  by  the  specific 
temperature  increase,  a  figure  will  be  obtained  by  which  the 
iodin  value  may  be  approximately  calculated. 

Klaidin  Test. — i  c.c.  of  mercury  is  dissolved  in  12  c.c. 
of  cold  nitric  acid  of  1.42  specific  gravity.  2  c.c.  of  the 
freshly -made  deep  green  solution  are  shaken  in  a  wide- 
mouthed  stoppered  bottle  with  50  c.c.  of  the  sample  to  be 
tested  and  the  agitation  repeated  every  ten  minutes  during 
two  hours.  When  treated  in  this  manner,  oils  consisting  of 
nearly  pure  olein  or  of  mixtures  of  olein  with  solid  esters, 
such  as  palmitin  and  stearin,  give  a  more  or  less  solid  product. 
Olive  oil  is  remarkable  for  the  canary  or  lemon-yellow  and 
great  firmness  of  the  mass  formed.  After  24  hours  the  hard- 
ness of  the  product  is  such  that  it  is  impervious  to  a  glass 
rod,  and  sometimes  rings  when  struck  ;  but  this  character  is 
also  possessed  by  the  elaidins  yielded  by  the  arachis  and  lard 
oils.  In  making  the  test,  it  is  important  to  note  the  time  re- 
quired to  obtain  a  "solid"  product,  which  will  not  move  on 
shaking  the  bottle,  as  well  as  the  ultimate  consistency.  The 
temperature  should  be  kept  nearly  constant,  or  erratic  results 
may  be  obtained. 

The  behavior  of  the  more  important  oils,  when  tested  in 
the  foregoing  manner,  is  described  by  A.  H.  Allen  as  fol- 
lows : 

A  hard  mass  is  yielded,  among  others,  by  olive,  almond, 
lard,  and  sometimes  arachis  oils. 

A  product  of  the  consistency  of  butter  is  given  by  mustard, 
and  sometimes  by  arachis  and  rape  oils. 

A  pasty  or  buttery  mass  which  separates  from  a  fluid  portion 


FATS    AND    OILS  157 

is  yielded  by  rape,  sesame,  cottonseed,  sunflower,  and  some- 
times mustard  oils.  Liquid  products  are  yielded  by  linseed, 
hempseed,  walnut,  and  other  drying  oils. 

The  results  of  the  elaidin  test  must  be  accepted  with  cau- 
tion, since  it  is  affected  by  many  conditions,  such  as  tempera- 
ture, shape  of  the  containing  vessel,  and  the  mode  of  prepa- 
ration of  the  nitrous  acid.  The  extent  to  which  the  sample 
has  been  exposed  to  light  and  air  is  a  still  more  important 
factor ;  it  has  been  shown  that  olive  oil  after  exposure  to  sun- 
light for  two  weeks  may  fail  to  respond  to  the  test. 

Index  of  Refraction. — This  datum  differs  notably  in  differ- 
ent oils,  but  it  is  not  of  much  value  in  detecting  adulteration 
unless  considerable  of  the  adulterant  be  present.  Several  in- 
struments have  been  devised  for  making  refraction  determina- 
tion ;  the  familiar  ones  are  the  refractometer  of  Abbe,  the 
oleorefractometer  of  Amagat  and  Jean,  and  the  butyrorefrac- 
tometer  of  Zeiss. 

The  oleorefractometer  consists  essentially  of  a  collimator,  a 
view-telescope,  and  a  vessel  to  contain  the  oil.  The  last  is 
provided  with  parallel  glass  slides,  and  in  the  center  is  a  vessel 
with  two  plate  glass  sides,  inclined  to  each  other  at  an  angle 
of  107°.  An  arbitrary  scale  is  placed  in  the  focus  of  the 
eye-piece,  and  the  reading  is  made  by  means  of  a  semicircular 
stop  in  the  collimator,  the  image  of  which  is  thrown  on  the 
scale  and  divides  the  field  into  a  dark  and  a  light  portion.  If 
the  outer  vessel  and  inner  prism  be  filled  with  the  same  oil, 
the  light  which  passes  through  will  not  be  refracted,  and  con- 
sequently no  alteration  of  the  position  of  the  image  will  take 
place.  If,  however,  the  inner  prism  be  filled  with  a  different 
oil,  refraction  will  take  place  and  the  line  dividing  the  field 
will  be  displaced  to  the  right  or  left.  The  instrument  is  fur- 
nished with  a  standard  oil,  said  to  be  sheepsfoot  oil,  for  use  in 
the  outer  vessel.  Instead  of  this,  the  oil  may  be  compared 
with  a  sample  of  the  same  kind  known  to  be  pure. 


158  FOOD    ANALYSIS 

The  butyrorefractometer  has  been  strongly  recommended 
for  the  examination  of  butter.  It  is  equally  adapted  for  the 
examination  of  fats  and  oils,  and  maybe  used  for  the  determ- 
ination of  the  index  of  refraction  as  well. 

Drying  Property. — Livache's  Test. — The  so-called  drying 
of  oils  (a  process  of  oxidation)  is  hastened  by  admixture  with 
finely  divided  lead.  This  is  prepared  by  precipitating  lead 
acetate  by  zinc,  washing  the  precipitate  rapidly  with  water, 
alcohol,  and  ether  in  succession,  and  drying  at  very  low  pres- 
sure. (Probably  drying  in  nitrogen  gas  would  be  preferable.) 
I  gram  of  the  dried  lead  is  mixed  on  a  watch-glass  with  not 
more  than  0.7  gram  of  the  sample  by  dropping  the  latter  so 
that  it  is  distributed  over  the  mass  of  the  lead.  The  glass  is 
allowed  to  stand  at  room  temperature  exposed  to  light,  but 
reasonably  protected  from  dust. 

Drying  oils  absorb  the  maximum  quantity  of  oxygen  after 
from  1 8  hours  to  3  days,  but  non-drying  oils  do  not  begin  to 
gain  weight  until  after  4  or  5  days.  Fat-acids,  except  those 
from  cottonseed  oil,  behave  the  same  as  the  fats.  Livache's 
results  are  given  in  the  following  table.  The  figures  show  the 
percentage  of  increase  in  weight  after  the  time  specified.  A 
drying  oil  (linseed)  is  added  for  comparison  with  the  food  oils. 
The  figure  for  maize  oil  is  given  by  Vulte  and  Gibson. 

OIL.  2  DAYS.  7  DAYS.  10  DAYS. 

Olive, o  1.7 

Cottonseed, 5.9 

Maize, 5-° 

Arachis,    .        o  1.8 

Sesame, o  2.4 

Rape, o  2.9 

Linseed,    .....    14.3 

Soluble  and  Insoluble  Acids. — This  method,  due  to  O. 
Hehner  and  A.  Angell,  has  been  much  modified  by  other  in- 
vestigators. The  proportion  of  acids  insoluble  in  water  is 
often  called  the  Hehner  value.  The  following  method,  de- 


FATS    AND    OILS  I  59 

scribed  by  A.  H.  Allen,  is  somewhat  different  from  that  rec- 
ommended by  the  A.  O.  A.  C,  but  will  serve  for  practical 
purposes,  it  being  understood  that  blank  tests  and  tests  with 
standard  oils  should  be  made  for  comparison  :  About  5  grams 
of  the  sample,  accurately  weighed,  are  placed  in  a  saponifica- 
tion  flask,  50  c.c.  of  a  solution  of  40  grams  of  sodium  hy- 
droxid  to  1000  c.c.  of  strong  alcohol  added,  the  flask  closed, 
and  the  mixture  heated  in  a  steam-bath  until  complete  saponi- 
fication  has  occurred.  The  flask  is  cooled,  the  soap  solution 
acidulated  with  sulfuric  acid,  the  aqueous  liquid  separated 
from  the  layer  of  fatty  acids,  and  the  latter  several  times 
boiled  with  a  considerable  quantity  of  water  in  a  flask  fur- 
nished with  a  reflux  condenser.  The  liquids  resulting  from 
these  operations  are  separated  from  the  insoluble  fatty  acids, 
which  it  is  desirable  to  boil  again  with  a  moderate  quantity  of 
water,  while  driving  a  current  of  steam  through  the  flask  in 
which  they  are  contained,  collecting  the  distillate,  and  treating 
it  like  the  washings.  The  acidulated  aqueous  liquid  first  sep- 
arated from  the  layer  of  fatty  acids  is  then  distilled  to  a  small 
bulk,  and  the  distillate  exactly  neutralized  with  standard  so- 
dium hydroxid,  using  phenolphthalcin  as  an  indicator.  The 
first  washings  from  the  insoluble  fatty  acids  are  then  added  to 
the  contents  of  the  distilling  flask,  and  the  liquid  again  dis- 
tilled to  a  small  bulk,  the  process  being  repeated  with  the 
succeeding  washings.  The  different  distillates  should  be 
titrated  separately  with  decinormal  alkali  and  phenolphthalein, 
so  that  the  progress  and  completion  of  the  washing  may  be 
followed,  and  some  information  obtained  as  to  the  nature  and 
relative  proportions  of  the  lower  fatty  acids  present. 

The  neutralized  distillates  should  be  united  and  evaporated 
gently  to  dryness,  and  the  residue  dried  at  100°  until  the 
weight  is  constant.  It  consists  of  the  sodium  salts  of  the 
acids  that  passed  over  in  the  distillation.  If  the  number  of 
cubic  centimeters  of  N  sodium  hydroxid  employed  for  neu- 


l6o  FOOD    ANALYSIS 

tralization  be  multiplied  by  0.22,  and  the  product  be  sub- 
tracted from  the  weight  of  the  dry  residue,  the  difference 
will  be  weight  of  the  volatile  acids. 

When  coconut  oil  and  palmnut  oil  are  treated  in  this  man- 
ner, the  distillate  will  be  found  to  contain  lauric  acid,  which, 
though  almost  insoluble  in  water,  is  volatile  in  a  current  of 
steam.  It  may  be  separated  from  the  more  soluble  volatile 
fatty  acids  by  filtering  the  distillate. 

Cholesterol  and  Phytosterol. — Most  vegetable  oils,  with 
the  notable  exception  of  olive  oil  and  palm  oil,  contain  a 
small  proportion  of  phytosterol.  Animal  oils  and  olive  oil, 
on  the  other  hand,  contain  cholesterol,  and  it  is  thought  to 
be  possible  to  distinguish  a  vegetable  oil  from  one  of  animal 
origin  by  the  isolation  and  identification  of  one  or  the  other 
of  these  bodies.  A  method  for  the  extraction  of  cholesterol 
and  phytosterol  is  that  of  A.  Foster  &  R.  Riechelmann  :  50 
grams  of  the  fat  are  twice  boiled,  for  about  30  minutes  at  a 
time,  with  75  c.c.  of  95  per  cent,  alcohol  in  a  flask  fitted 
with  a  reflux  condenser,  the  flask  being  meanwhile  well 
shaken.  The  alcoholic  solution  is  mixed  with  15  c.c.  of  30 
per  cent,  sodium  hydroxid  solution,  and  boiled  on  the  water- 
bath  in  a  flask  fitted  with  a  condensation  tube  until  about  one- 
fourth  of  the  alcohol  is  evaporated.  The  fluid  is  then  evap- 
orated nearly  to  dryness  in  a  porcelain  basin  and  the  residue 
shaken  with  ether.  The  ethereal  solution  is  evaporated  to 
dryness,  the  residue  treated  with  a  little  ether,  filtered,  evap- 
orated, and  the  residue  crystallized  from  95  per  cent,  alcohol. 

Von  Raumer  determines  the  amount  of  crude  cholesterol 
and  phytosterol  in  fats  as  follows  :  50  grams  of  the  oil  are 
saponified  with  alcoholic  potassium  hydroxid.  The  resulting 
soap  is  evaporated  to  dryness,  reduced  to  powder,  and  ex- 
tracted with  50  to  75  c.c.  of  ether  in  a  Soxhlet  apparatus, 
plugs  of  fat-free  cotton  being  placed  above  and  below  the 
layer  of  soap.  The  residue  is  saponified  again  with  10  c.c. 


FATS    AND    OILS  l6l 

of  half  normal  alkali,  evaporated  to  dryness  with  sand,  and 
re-extracted  as  before  during  two  hours.  When  the  work  is 
carefully  done,  the  second  saponification  and  extraction  is  un- 
necessary. 

The  following  amounts  of  residue  were  obtained  from  100 
grams  of  oil  :  Cottonseed  oil,  0.719  gram  ;  sesame  oil,  1.314 
grams  to  1.325  grams  ;  lard,  0.217  gram. 

Pure  cholesterol  can  easily  be  distinguished  from  phyto- 
sterol  by  the  form  and  grouping  of  the  crystals.  If  both 
bodies  are  present,  the  mixture  crystallizes  in  one  form  only, 
the  crystals  either  approximating  to  the  form  of  phytosterol 
or,  if  cholesterol  be  present  in  the  greater  quantity,  differing 
from  the  pure  crystals  of  either  body. 

Clwlesterol  is  insoluble  in  water,  sparingly  soluble  in  cold 
alcohol,  but  dissolves  readily  in  ether,  chloroform,  petro- 
leum spirit,  and  carbon  disulfid.  It  crystallizes  in  anhydrous 
needles  of  melting-point  147°,  but  from  its  hot  alcoholic 
solution  it  is  deposited  in  laminae  composed  of  extremely  thin 
rhombic  plates,  often  showing  reentering  angles.  A  delicate 
test  for  cholesterol  is  that  of  Hager,  as  modified  by  Salkow- 
ski :  A  few  centigrams  of  cholesterol  are  dissolved  in  2  c.c. 
of  chloroform,  an  equal  volume  of  sulfuric  acid  is  added, 
and  the  mixture  shaken.  The  chloroform  solution  immedi- 
ately becomes  blood-red,  afterward  cherry-red  and  purple  ; 
this  last  tint  remains  for  several  days.  The  sulfuric  acid 
layer  under  the  chloroform  shows  a  strong  green  fluorescence. 
On  pouring  a  few  drops  of  the  purple  chloroform  layer  into 
a  porcelain  basin,  the  red  color  changes  rapidly  to  blue,  green, 
and  finally  to  yellow.  On  diluting  the  purple  chloroform 
solution  with  more  chloroform,  it  becomes  nearly  colorless, 
or  acquires  an  intense  blue  ;  if  it  now  be  shaken  again  with 
the  sulfuric  acid  layer,  the  former  coloration  appears.  These 
changes  of  color  are  due  to  traces  of  water  in  the  chloro- 
form. 


1 62  FOOD    ANALYSIS 

Phytosterol  resembles  cholesterol,  but  differs  from  it  in  crys- 
talline form  and  in  melting-point.  From  a  hot  alcoholic  solu- 
tion phytosterol  crystallizes  in  solid  needles  grouped  in  tufts. 
Under  the  microscope  these  appear  as  long  solid  needles 
arranged  in  star  or  bunch-like  groups.  Like  the  cholesterol 
crystals,  these  contain  a  molecule  of  water,  but  they  melt  at 
132°  to  134°.  (Bomer  gives  a  mean  melting-point  of  137°, 
but  this  figure  requires  confirmation.) 

The  solution  of  phytosterol  in  chloroform  gives  the  same 
reaction  with  sulfuric  acid  as  does  cholesterol,  but  there  is  the 
slight  difference  that  the  coloration  obtained  with  the  former 
passes  after  a  few  days  into  a  bluish-red,  whereas  the  choles- 
terol solution  remains  more  of  a  cherry-red. 

Acetyl  Value. — This  determination,  originally  suggested 
by  Benedikt,  is  most  conveniently  carried  out  by  the  method 
of  J.  Lewkowitsch  20  :  10  grams  of  the  sample  are  boiled  for 
two  hours  with  an  equal  volume  of  acetic  anhydrid  in  a  flask 
provided  with  an  inverted  condenser ;  the  mass  is  then  trans- 
ferred to  a  larger  beaker,  diluted  with  several  hundred  cubic 
centimeters  of  water,  and  boiled  for  30  minutes,  with  a  slow 
current  of  carbon  dioxid  passed  through  by  means  of  a  tube 
drawn  out  at  the  lower  end  to  a  fine  opening.  This  prevents 
bumping.  On  cooling,  two  layers  are  formed.  The  water- 
layer  is  drawn  off  by  a  siphon  and  the  other  portion  washed 
three  times  by  boiling  with  convenient  measures  of  water. 
Prolonged  washing  should  be  avoided.  The  acetylated  prod- 
uct is  freed  from  water  by  filtration  through  a  dry  filter  in  a 
water-oven  at  100°. 

5  grams  of  the  substance  are  saponified  as  noted  on  page 
148,  the  alcohol  is  evaporated,  and  the  soap  dissolved  in 
water.  The  subsequent  operations  may  now  be  completed  by 
two  methods,  "  distillation  "  or  "filtration."  The  latter  is 
the  shorter  and  more  convenient. 

Distillation  Method. — The  liquid  is  made  up  to  a  volume  of 


FATS    AND    OILS  163 

several  hundred  cubic  centimeters  in  a  flask  fitted  with  an 
arrangement  for  passing  in  steam  or  for  adding  water  from 
time  to  time.  Sufficient  dilute  sulfuric  acid  (i  part  of  acid 
to  10  of  water)  is  added  to  make  the  liquid  slightly  acid,  and 
distillation  is  carried  on  until  about  700  c.c.  are  collected. 
The  distillate  is  filtered  and  titrated  with  decinormal  alkali. 
Phenolphthalein  is  recommended  as  an  indicator,  but  probably 
methyl-orange  will  serve  as  well.  The  number  of  cubic  cen- 
timeters of  solution  required  to  neutralize  the  distillate,  mul- 
tiplied by  5.61  and  the  product  divided  by  the  weight  of  the 
acetylated  material,  gives  the  acetyl  number. 

Filtration  Method. — The  solution  of  the  saponified  acetyl- 
ated substance  is  mixed  with  sufficient  standard  sulfuric  acid 
just  sufficient  to  neutralize  the  alkali  added  for  saponification, 
and  the  mixture  warmed  gently.  The  acids  will  separate  as 
an  oily  layer.  The  layer  is  removed,  washed  with  boiling 
water  until  the  washings  are  not  acid,  titrated  with  decinormal 
alkali,  and  the  acetyl  number  calculated  as  above. 

The  acetyl  number  is  the  number  of  milligrams  of  potas- 
sium hydroxid  required  for  neutralizing  the  acetic  acid  ob- 
tained from  i  gram  of  the  acetylated  substance. 

In  this  process  cholesterol  and  phytosterol  are  included  in 
the  acetylization. 

Substances  yielding  volatile  acids  give  an  acetyl  number 
too  high  ;  this  condition  will  affect  the  distillation  method 
more  than  the  filtration  method.  To  eliminate  most  of  this 
error,  the  percentage  of  volatile  acid  should  be  determined 
and  the  figures  obtained  deducted  from  the  acetyl  number. 

The  water  used  in  both  methods  should  be  freed  as  far  as 
possible  from  carbon  dioxid.  Even  the  water  used  in  pro- 
ducing the  open  steam  should  be  brought  to  active  boiling 
before  the  steam  is  let  into  the  flask.  Waters  rich  in  car- 
bonate are  especially  objectionable.  A  slight  excess  of  sul- 
furic acid  causes  the  insoluble  acids  to  separate  better,  but 


164  FOOD    ANALYSIS 

this  must,  of  course,  be  known  accurately  and  allowance 
made  for  it. 

It  is  possible  that  the  data  elucidated  by  H.  D.  Richmond 
with  regard  to  the  rate  of  distillation  of  acids  of  the  acetic 
series  could  be  applied  to  the  distillation  method  with  advan- 
tage, but  a  special  investigation  will  be  needed  to  determine 
the  point. 

Viscosity. — Practical  determinations  of  viscosity  are  com- 
parative only  and  are  of  little  value  unless  uniform  methods 
are  employed.  Many  forms  of  viscosimeter  have  been  de- 
vised. The  only  form  we  can  recommend  for  general  use  is 
the  torsion  viscosimeter  devised  by  O.  S.  Doolittle.  A  de- 
scription of  the  instrument  and  its  use  is  unnecessary,  as  it  is 
made  according  to  standard  patterns  and  full  working  direc- 
tions are  furnished  with  it. 

W.  C.  Blasdale  investigated  the  relative  viscosities  of  solu- 
tions of  soap  from  different  grades  of  olive  oils  and  found  the 
figures  of  much  value.  He  used  the  torsion  viscosimeter. 
The  preparation  of  the  solution  is  as  follows  :  1 5  grams  of 
the  sample  are  saponified  with  a  mixture  of  10  c.c.  of  alcohol 
and  30  c.c.  of  water  containing  7.5  grams  of  potassium  hy- 
droxid.  The  mass  is  washed  into  a  large  dish,  heated  until 
the  alcohol  is  removed,  diluted  to  500  c.c.  at  20°,  and  the 
viscosity  determined.  The  result  is  expressed  by  Blasdale  in 
the  number  of  grams  of  sugar  that  it  would  be  necessary  to 
add  to  a  liter  of  water  to  get  the  same  readings.  With  some 
oils  it  would  be  necessary  to  dilute  the  solution  to  1000  c.c. 

Blasdale's  results  were  as  follows  : 

OILS.  VISCOSITY. 

Olive  (California), 573-655 

Cottonseed, 280 

Arachis, 220 

Sesame, 4' 5 

Rape 670 

Sweet  almond, 645 


FATS    AND    OILS 


i65 


Mustard-seed  oils  give  high  viscosity  figures,  and  a  mixture 
of  these  with  cottonseed  oil  in  some  proportions  would 
escape  recognition  by  this  test. 

Unsaponifiable  Matter. — Most  fats  and  oils  contain  ap- 
preciable amounts  of  unsaponifiable  substances,  but  the 
determination  of  them  is  of  value  principally  in  detecting 
adulteration  with  mineral  oil  and  paraffin.  In  many  cases 
saponification  and  solution  of  the  soap  in  water  will  not 
suffice  for  separation,  and  the  routine  method 
devised  by  A.  H.  Allen  must  be  followed  : 

5  grams  of  the  sample  are  saponified,  the 
solution  freed  from  alcohol  if  any  has  been 
used,  and  transferred  to  a  stoppered  separator 
(Fig.  44)  of  200  c.c.  capacity,  the  exit  tube 
of  which  is  cut  off  obliquely.  The  mass  is 
diluted  with  water  to  about  80  c.c.,  60  c.c.  of 
ether  added,  the  vessel  closed,  well  shaken, 
and  allowed  to  rest.  Separation  does  not 
always  occur  readily,  but  may  often  be  induced 
by  cooling  the  contents,  by  adding  a  little 
sodium  hydroxid  solution,  more  ether,  or  a 
few  cubic  centimeters  of  alcohol  and  rotating 
the  mass  gently.  The  aqueous  liquid  is  run  FIG.  44. 

out,  a  few  drops  of  sodium  hydroxid  solution 
and  10  c.c.  of  water  are  added,  gently  agitated,  and  run  off. 
This  treatment  is  repeated,  after  which  the  ether  is  run  off  in 
a  tared  flask,  the  aqueous  liquid  is  agitated  with  a  fresh  por- 
tion of  ether,  which  is  washed  and  poured  into  the  tared  vessel 
as  before.  This  process  is  again  performed,  when  it  will  be 
complete.  The  ethereal  solution  will  often  be  fluorescent. 
The  greater  portion  of  the  ether  should  be  distilled  off  in  a 
recovering  apparatus  and  the  rest  evaporated  in  the  water- 
bath.  If  the  mass  retains  globules  of  water,  the  flask  should 
be  held  horizontally  and  rotated  rapidly  so  as  to  spread  the 

l 

UN1V_  V    J 


1 66  FOOD    ANALYSIS 

residue  in  a  thin  layer.  When  no  more  water  is  visible  and 
the  odor  of  ether  is  very  slight,  the  flask  is  placed  on  its  side 
in  the  water-oven  for  I  5  minutes,  cooled,  and  weighed. 

Long  heating  should  be  avoided,  as  some  hydrocarbons  are 
sensibly  volatile  at  100°.  Spermaceti  and  waxes  yield  in 
this  process  a  large  percentage  of  unsaponifiable  matter,  hence 
it  is  not  available  for  the  detection  of  paraffin  in  such  sub- 
stances. 

In  ordinary  cases  the  distribution  of  the  bodies  will  be  as 
follows.  Many  resins  will  pass  into  the  water  in  the  form  of 
sodium  salts  : 


IN  THE  ETHER  :  IN  THE  WATER  : 

Hydrocarbons.  Sodium  salts. 

Mineral  oils.  Glycerol. 

Paraffin.  Sodium  hydroxid. 

Neutral  resins. 

Coloring-matters  from  palm  oil. 
Phytosterol. 
Cholesterol. 


ANALYTIC  DATA. — The  data,  commonly  termed  "  con- 
stants," obtained  by  the  processes  described  in  the  preceding 
pages,  are  subject  to  uncertainty,  owing  to  the  want  of  abso- 
lute standards.  Fats  and  oils,  especially  the  latter,  being 
mixtures  of  several  ingredients,  will  vary  with  conditions  of 
growth  of  the  animals  or  plants  yielding  them,  methods  of 
extracting  and  refining,  exposure  to  light,  heat,  and  air,  and, 
doubtless,  from  unrecognized  causes.  Samples  prepared  in 
the  laboratory  do  not  necessarily  serve  as  standards  for  com- 
mercial products.  Errors  of  observation  from  defective  ap- 
paratus, especially  inaccurate  thermometers,  are  by  no  means 
uncommon. 

The  data  for  specific  gravity  and  for  melting  and  solidifying 
points  given  in  the  following  tables  have  been  compiled  from 
the  best  accessible  sources,  and  will  give  a  general  idea  of  the 
range  of  figures  in  commercial  samples  : 


FATS    AND    OILS 


i67 


SPECIFIC  GRAVITIES  OF  FATS  AND  OILS  AND  OF  ACIDS 
DERIVED  FROM  THEM 


OILS. 


Olive,    ..........  0.914-0.918 

Cottonseed,      .......  0.922-0.930  0.8725 

Maize,  ..........  0.916-0.926  0.8711 

Coconut,   .........  0.925  (at  18°;  0.868-0.874 

Arachis,        ........  0.916-0.922 

Sesame,     .........  0.921-0.924 

Rape,    ..........  0.913-0.917 

Cacao-butter,    .    ......  0.945-0.976  0.857 

Lard,    .    .    ........  0.931-0.938  0.859-0.864 

Tallow,     .........  0.893-0.898 

Butter-fat,     ........  0.926-0.940  0.909-0.914 

Coconut  olein,      ......        0.926  0.907 


ACIDS. 
(iooP.) 
0.875 
0.882 

0.844 
0.847 

0.875-0.879 

0.837-0.840 
0.870 


MELTING  AND  SOLIDIFYING  POINTS  OF  FATS  AND  OILS. 
MELTING-POINTS  AND  TITER-TESTS  OF  ACIDS 

The  liter-tests  were  determined  by  J.  Lewkowitsch. 


OIL  OR  FAT. 


ACIDS. 


Melting- 
point. 

Olive, 

Cottonseed,     .    .    . 

Maize, 

Coconut, 20  to  28 

Arachis, 

Sesame, 

Rape, 

Cacao-butter,      .    .    .  30  to  34 

Lard 28  to  45 

Butter-fat,  ...  .  29  to  35 
Beef  tallow,  .  .  .  .361049 
Mutton  tallow,  .  .  .  36  to  49 


Solidifying- 

point. 

Melting-point. 

Titer-test. 

4  to  —  2 

24  to  27 

16.9  to  26.4 

I  to  IO 

35  to  40 

32.2  to  37.6 

not  above  —  IO 

18  to  20 

14  to  23 

24  to  27 

21.2  to  25.2 

—5 

28  to  33 

28.1  to  29.2 

—  4  to  —  6 

23  to  31 

21.2  to  23.8 

—  6  to  —  10 

18  to  22 

11.7  to  13.6 

20  to  27 

48  to  52 

48.0  t048.2 

27  to  44 

35  to  47 

41.4  to  42.0 

20  to  30 

36  to  46  (insol.) 

33  ^  48 

43  to  47 

37.9  1046.2 

33  to  48 

46  to  54 

40.1  1048.3 

IODIN  NUMBERS  OF  FATTY  ACIDS 
OIL  OR  FAT.  MIXED  ACIDS.  LIQUID  ACIDS. 

Olive, 86-90 

Cottonseed, Ill-li6  147 

Maize 113-125  140 

Arachis, 95-103  128 

Sesame, 109-112 

Rape, 99-105 

Coconut, 8.5-9  54 

Cacao-butter, 32-5~39 

Butter-fat, 28-31 

Lard, 64-81  104 


i68 


FOOD    ANALYSIS 


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FATS    AND    OILS  169 

SPECIAL  TESTS. — Several  tests  are  of  value  for  recognizing 
particular  oils  or  fats.  The  indications  for  their  use  will  be 
given  in  connection  with  them. 

Carbon  Disulfid-sidfur  Test. — Halpheris  Test. — This  is  in- 
tended for  the  recognition  of  cottonseed  oil.  It  is  applicable 
both  to  oils  and  to  the  separated  acids.  The  operation  is  as 
follows  : 

Carbon  disulfid  containing  about  I  per  cent,  of  sulfur  in 
solution  is  mixed  with  an  equal  volume  of  fusel  oil.  Equal 
volumes  of  this  reagent  and  the  sample  (about  3  c.c.  of  each) 
are  mixed  and  heated  in  a  bath  of  boiling  brine  for  I  5  min- 
utes. If  no  red  or  orange  tint  is  produced,  I  c.c.  of  the  re- 
agent is  added,  and  if  after  5  or  10  minutes  more  heating  no 
color  is  shown,  a  third  addition  of  I  c.c.  may  be  made.  .It  is 
possible  to  detect  very  small  quantities  of  cottonseed  oil  by 
this  test.  Lard  and  lard  oil  derived  from  animals  fed  on  cot- 
tonseed meal  will  often  give  a  faint  reaction. 

Silver  Nitrate  Test. — Bechi's  Test. — This  is  a  test  for  cotton- 
seed oil.  Several  modifications  are  in  use.  According  to  Del 
Torre,  the  following  reagents  are  required  : 

I. 

Silver  nitrate, i.o  gram. 

Alcohol,  98  per  cent,  (by  vol.), 200.0  c.c. 

Ether, 40.0  c.c. 

Nitric  acid, O.I  gram. 

II. 

Fusel  oil, loo.o  c.c. 

Rapeseed  oil, 15.0  c.c. 

10  c.c.  of  the  oil  to  be  examined  are  mixed  in  a  test-tube 
with  i  c.c.  of  reagent  I,  and  then  shaken  with  10  c.c.  of  re- 
agent II.  The  mixture  is  next  divided  into  two  equal  por- 
tions, one  of  which  is  immersed  in  boiling  water  for  1 5  min- 
utes. The  heated  sample  is  then  removed  from  the  water- 
bath,  and  its  color  compared  with  the  unheated  half.  Cotton- 
15 


I/O  FOOD    ANALYSIS 

seed  oil  is  indicated  by  the  reddish-brown  of  the  heated 
portion.  Only  the  purest  alcohol  should  be  used,  and  the 
rapeseed  oil  used  should  be  "  cold  drawn,"  and  only  slightly 
colored  ;  it  should  be  filtered  in  a  hot-water  oven  before  pre- 
paring the  reagent.  To  guard  against  errors  from  impurity 
of  the  reagents,  a  blank  test  should  be  made. 

It  is  stated  that  old  and  rancid  samples  will  not  react  unless 
the  rape  oil  be  present.  Most  chemists,  however,  do  not  use 
it,  especially  in  testing  lard.  O.  Hehner  uses  reagent  I,  add- 
ing I  volume  to  2  volumes  of  oil  and  heating  for  1 5  minutes. 
Milliau  applies  the  silver  solution  (No.  I)  to  the  mixed  fatty 
acids  ;  but  experience  has  shown  that  in  some  cases,  in  which 
cottonseed  oil  was  present  and  responded  to  the  test,  the  fatty 
acids  failed  to  give  a  similar  reaction.  After  heating  to  240° 
or  on  long  keeping,  the  oil  or  fatty  acids  fail  to  respond  to 
the  test. 

Furfural  Test. — Baudouin' s  Test. — This  is  a  test  for  sesame 
oil.  In  its  original  form,  the  sample  was  shaken  with  a  mix- 
ture of  sucrose  and  strong  hydrochloric  acid,  when  a  crimson 
is  produced  if  sesame  oil  be  present.  As  furfural  is  a  prod- 
uct of  the  action  of  hydrochloric  acid  on  sucrose,  and  is  the 
active  agent  in  the  test,  Villavecchia  and  Fabris  have  substi- 
tuted an  alcoholic  solution  of  the  latter  for  the  sugar.  The 
solution  is  made  dilute  (2  per  cent.),  as  furfural  itself  gives  a 
violet  tint  with  hydrochloric  acid.  The  modified  test  is 
applied  in  one  or  the  other  of  the  following  forms  : 

(a)  o.  I  c.c.  of  the  2  per  cent,  furfural  solution  is  placed  in 
a  test-tube,  10  c.c.  of  the  sample  and  10  c.c.  of  hydrochloric 
acid  (sp.  gr.  1.19)  added,  the  mixture  shaken  for  half  a  min- 
ute, and  allowed  to  settle.  In  the  presence  of  even  less  than 
I  per  cent,  of  sesame  oil,  the  aqueous  layer  will  become 
crimson.  In  the  absence  of  sesame  oil  the  lower  layer  is 
either  colorless  or,  at  most,  becomes,  as  in  the  case  of  very 
rancid  though  pure  olive  oil,  dirty  yellow. 


OLIVE    OIL  I/I 

(//)  o.i  c.c.  of  the  furfural  solution  is  mixed  with  10  c.c.  of 
the  sample  and  I  c.c.  only  of  hydrochloric  acid  added  ;  the 
mass  shaken  thoroughly  and  separation  brought  about  by 
addition  of  10  c.c.  of  chloroform,  or  by  a  centrifuge,  when 
the  aqueous  layer  will  be  crimson  with  even  less  than  i  per 
cent,  of  sesame  oil. 


OLIVE  OIL 

Olive  oil  is  obtained  from  the  fruit  of  the  Olea  europcea  L. 
Its  color  ranges  from  light  yellow  to  golden  yellow,  but  some 
forms  are  deep  green  from  presence  of  chlorophyl.  The  quality 
of  the  oil  depends  on  many  conditions  ;  that  intended  for  food 
is  always  expressed  cold. 

Olive  oil  contains  about  28  per  cent,  of  solid  fat,  consisting 
of  palmitin  and  a  little  arachidin.  The  remainder  is  mostly 
olein,  with  a  little  linolin.  O.  Hehner  and  C.  A.  Mitchell 
found  no  stearin.  Appreciable  amounts  of  cholesterol  are 
present,  differing  from  most  vegetable  oils,  which  contain 
phytosterol.  The  unsaponifiable  matter  ranges  from  I  to  1.5 
per  cent.  Free  fatty  acid  is  always  present,  amounting  in  the 
best  grades  to  about  1.5  per  cent.,  and  in  the  lowest  grades 
to  25  per  cent. 

Adulteration. — Olive  oil  is  very  liable  to  adulteration.  In 
this  country,  cottonseed  oil  and  arachis  oil  are  the  additions 
most  commonly  employed.  In  many  cases  the  article  con- 
tains no  olive  oil,  cottonseed  oil  or  a  mixture  of  cottonseed 
and  arachis  oil  being  substituted.  Other  adulterants  are 
sesame,  rape,  poppyseed,  and  lard  oil.  Still  more  rarely, 
curcas  oil,  and  even  castor  oil  have  been  employed.  It  is 
stated  that  15  or  20  per  cent,  of  the  latter  may  be  present 
without  affecting  the  taste.  In  the  lower  grades  of  oil,  not 
intended  for  table  use,  any  ordinary  oil,  including  refined 
petroleum,  may  be  present. 


1/2  FOOD    ANALYSIS 

Specific  Gravity. — The  specific  gravity  of  olive  oil  usually 
ranges  from  0.914  to  0.917,  or  even  0.918  in  the  case  of 
California  oils.  Commercial,  usually  brown,  oils,  expressed 
at  a  high  temperature,  and  containing  a  higher  proportion  of 
palmitin,  may  range  as  high  as  0.925.  A  specific  gravity  of 
0.918  or  over,  in  a  sample  of  light  color,  would  give  rise  to 
suspicion  of  adulteration  with  cottonseed,  poppy  seed,  or 
sesame  oil. 

Solidifying-point. — Olive  oil  has  usually  a  higher  solidifying- 
point  than  any  other  of  the  vegetable  oils.  Mixtures  of  olive 
with  other  oils  have,  as  a  rule,  a  lower  melting-point  than 
either  constituent  alone.  The  melting  and  solidifying  points 
of  the  mixed  acids  are  also  of  some  value,  but,  according  to 
Dieterich,  less  than  25  per  cent,  of  adulteration  cannot  be 
detected  with  certainty. 

Saponification  Value. — This  determination  is  of  use  only  in 
the  case  of  adulteration  with  a  considerable  proportion  of 
rape  oil. 

lodin  Number. — This  determination  furnishes  the  most 
valuable  indications  of  the  purity  of  olive  oil.  The  figure 
for  pure  oil  usually  ranges  between  81.5  and  85  per  cent. 
Values  as  high  as  88.6  have  been  reported  from  some  Cali- 
fornia oils,  but  such  samples  are  exceptional,  and  a  figure 
above  85  should  give  rise  to  suspicion  of  adulteration. 

Heat  of  Br animation. — Specific  Temperature  Reaction. — The 
thermal  values  of  olive  oil  are  lower  than  those  of  other  vege- 
table oils  and  the  determination  is  frequently  of  use.  The 
following  is  a  list  of  determinations  adapted  to  detection  of 
the  particular  adulterants  noted  : 

COTTONSEED  OIL.  Halphen's  test ;  nitric  acid  color  test ; 
Bechi's  test ;  iodin  number  ;  Livache's  test ;  temperature  re- 
actions ;  viscosity  of  soap  solution. 

ARACHIS  OIL.  Viscosity  of  soap  solution ;  determination 
of  arachidic  acid  ;  iodin  number. 


OLIVE    OIL  1/3 

RAPE  OIL.  lodin  number  ;  melting  and  solidifying  of 
acids  ;  acetic  acid  test  ;  refractive  power. 

SESAME  OIL.  Furfural  test  (p.  170)  ;  iodin  absorption  ; 
temperature  reactions  ;  saponification  value. 

LARD  OIL.  Melting-point  of  fatty  acids  ;  odor  of  lard  on 
warming. 

Seed  Oils  Generally.     Separation  of  phytosterol. 

CASTOR  OIL.  Solubility  in  acetic  acid  in  the  cold  ;  solubil- 
ity in  absolute  alcohol  ;  specific  gravity. 

CURCAS  OIL.  Iodin  value  ;  saponification  value  ;  treated 
with  nitric  acid  and  copper,  intense  reddish-brown  is  pro- 
duced in  presence  of  even  10  per  cent,  of  curcas  oil. 

HYDROCARBON  OILS.  Determination  of  unsaponifiable  mat- 
ter (p.  165). 

Green  olive  oil  has  been  imitated  by  coloring  other  oils 
with  copper  acetate.  All  green  oils  should  be  tested  for  cop- 
per by  boiling  with  hydrochloric  acid  and  testing  the  acid 
solution,  as  described  on  p.  70. 

Elaidin  Test.  —  Olive  oil  yields  the  hardest  elaidin  of  all  the 
oils,  and  in  the  shortest  time,  but,  as  noted  on  page  156,  too 
much  reliance  must  not  be  placed  upon  the  indications  of 
this  test.  The  following  figures,  obtained  by  Blasdale  from 
California  oils,  serve  to  show  the  extent  to  which  time  re- 
quired to  form  a  solid  product  may  vary  in  even  fresh  sam- 
ples of  known  purity  : 


Uvaria,  ................     6  hours 

Pendulina,  .................     4     " 

Redding  Pecholine,    .............     3     " 

Nevadillo  bianco,  ..............     2     " 

Manzanillo,     ................  30  minutes 


Refractive  Power.  —  The  refractive  power  of  olive  oils  is 
less  than  that  of  any  other  of  the  vegetable  oils.  The  deter- 
mination of  the  refractive  index  gives  reliable  indications  only 


FOOD    ANALYSIS 

in  the  presence  of  a  considerable  proportion  of  the  adul- 
terant. More  satisfactory  results  are  said  to  be  obtained  by 
the  use  of  the  oleorefractometer  of  Amagat  and  Jean,  or 
of  the  Zeiss  butyrorefractometer.  Oliveri  has  determined 
the  degree  of  refraction  (in  the  oleorefractometer)  of  106  pure 
olive  oils,  and  compared  the  results  with  those  from  other 
oils,  as  follows  : 

DEGREE  OF  REFRACTION. 

Olive  oil, o  to  2 

Cottonseed  oil, 18.0 

Sesame  oil, 15.5 

Colza  oil, 26. 5 

Arachis  oil,       7.5 

Poppyseed  oil, 28.5 

Oliveri  concludes  from  his  figures  that  admixtures  of  not 
too  small  quantities  of  any  of  the  above  oils  can  be  detected, 
as  the  degree  of  refraction  would  be  above  2.  Arachis  oil 
might,  however,  easily  escape  detection. 

Nitric  Acid  Test. — This  will  detect  as  little  as  3  per  cent,  of 
cottonseed  oil  in  olive  oil.  Some  operators  employ  acid  of 
1.41  specific  gravity,  but,  according  to  J.  Lewkowitsch,  one 
of  1.375  gives  better  results.  He  recommends  that  the  mix- 
ture be  allowed  to  stand  about  24  hours,  when  olive  oil  con- 
taining cottonseed  oil  becomes  pure  brown  ;  but  if  rape  oil 
be  present,  the  mixture  becomes  more  yellowish.  Attention 
has  been  called  to  the  fact  that  some  highly  purified  cotton- 
seed oils  react  so  faintly  with  nitric  acid  that  samples  contain- 
ing as  much  as  10  per  cent,  showed  no  reaction. 

Halphen's  Test. — This  is  a  characteristic  test  for  detecting 
cottonseed  oil,  and  is  applicable  to  oils  that  have  been  heated 
for  a  short  time  to  240°,  also  to  the  fatty  acids.  Oils  that 
have  been  exposed  for  a  long  time  to  light  and  air  may  fail 
to  respond  to  the  test. 


COTTONSEED    OIL 


COTTONSEED  OIL 

Cottonseed  oil  is  obtained  from  seeds  of  several  species  of 
Gossypium.  The  crude  product  is  dark  red.  It  is  refined  by 
treatment  with  alkali,  by  which  some  soap  is  formed  that 
carries  with  it  the  coloring-matter.  The  refined  oil  is  pale 
yellow,  of  pleasant  flavor,  and  neutral,  but  becomes  rancid 
gradually,  when  free  acid  is  also  formed  and  a  so-called 
"stearin  "  deposited.  The  better  grades  of  oil  are  sold  after 
being  freed  from  stearin  by  chilling  or  long  standing.  The 
refined  oil  is  much  used  for  cooking  purposes  and  as  a  salad 
oil,  but  its  chief  uses  are  as  an  adulterant  for  olive  oil,  butter, 
lard,  and  lard  oil,  and  in  the  manufacture  of  butter  substitutes. 
It  is  so  cheap  that  it  is  but  little  liable  to  adulteration,  except 
possibly  with  mineral  oils. 

Cottonseed  oil  contains  stearin,  palmitin,  olein,  and  linolin. 
A  small  proportion  of  a  hydroxy-ester  is  said  to  be  present. 

Cottonseed  Stearin.  —  This  is  a  commercial  name  of  the  solid 
fat  deposited  on  standing  or  by  cooling  the  oil  and  pressing. 
The  product  so  obtained  varies  according  to  the  completeness 
with  which  the  oil  has  been  separated.  The  proportion  of 
true  stearin  appears  to  be  very  low.  A  sample  examined  by 
O.  Hehner  and  C.  A.  Mitchell  yielded  only  3  per  cent,  of 
stearic  acid.  As  ordinarily  obtained  the  fat  is  light  yellow 
and  of  the  consistency  of  butter.  It  is  largely  used  in  the 
preparation  of  substitutes  for  butter  and  lard. 

Another  variety  of  so-called  cottonseed  stearin  is  the  solid 
portion  of  the  fatty  acids  separated  from  the  oil  in  the  pro- 
cess of  purification  by  alkali.  It  consists  chiefly  of  stearic 
acid  and  is  employed  in  soap-making. 

The  following  are  some  of  the  physical  and  chemical  con- 
stants of  the  neutral  fat  first  described  : 

Specific  gravity,    •    •  jf|J  =  0.923     ^0  =  0.864  to  0.869    %£. 
Solidifying-point,     .  26°  1040°;    liter  test,  16°. 
Saponification  value,  194-195. 
lodin  value,  ....  89-104. 


FOOD    ANALYSIS 

MIXED  FATTY  ACIDS. 

Solidifying-point, 35°. 

Melting-point, 27°  to  30°. 

lodin  number, 94. 

Cottonseed  stearin  responds  to  the  color  tests  for  cottonseed 
oil. 

MAIZE  OIL     CORN  OIL 

.  Maize  oil  is  obtained  by  expression  from  the  seeds  of  the 
Zea  mays  L.,  either  directly  or  after  they  have  been  used 
for  the  preparation  of  alcohol.  The  latter  product  contains 
much  free  acid.  The  most  recent  and  extended  investi- 
gation of  this  oil  is  that  made  by  H.  T.  Vulte  and  H.  W. 
Gibson.2 1  Data  furnished  by  them,  together  with  some  from 
other  sources,  have  been  incorporated  in  the  tables  on  pages 
167  and  1 68.  The  following  additional  figures  are  all  from 
the  paper  of  Vulte  and  Gibson  : 

Index  of  refraction  (Abbe  refractometer),  .     1.4766 

Acid  value, 2.25 

Free  acid  (percentage), 1.12 

Insoluble  acid, 92.2 

Elaidin  test, Orange-yellow  deposit. 

Bechi's  test, Dark  brown. 

Many  esters  are  present,  as  the  following  acids  have  been 
obtained  from  the  saponified  material  :  Formic,  acetic,  stearic, 
palmitic,  arachidic,  hypogeic,  oleic,  linolic,  ricinolic  (probably), 
and,  according  to  some  investigators,  caproic,  caprylic,  and 
capric.  The  results  of  different  investigators  do  not  agree  in 
some  points.  O.  Hehner  and  C.  A.  Mitchell  were  unable  to 
find  stearin  in  a  sample  examined  by  them.  J.  C.  Smith  found 
volatile  acids  equivalent  to  a  Reichert  number  between  2  and 
3.  C.  G.  Hopkins  found  no  volatile  acids  in  the  sample  exam- 
ined by  him. 

The  oil  is  practically  without  drying  power  at  the  ordinary 
temperature.  According  to  J.  C.  Smith,  no  decided  siccative 


ARACHIS    OIL 

properties  are  communicated  to  it  by  simply  "  boiling  "or  by 
the  addition  of  litharge.  On  passing  a  current  of  air  through 
it  for  an  hour  at  a  temperature  of  150°,  it  becomes  slightly 
darker  and  rather  more  viscous,  but  not  to  the  same  extent  as 
cottonseed  oil.  If  to  the  oil  so  treated  a  small  quantity  of 
manganese  borate  be  added,  slight  siccative  properties  are  ac- 
quired, and  a  thin  film  on  lead  dries  in  from  10  to  20  hours, 
but  not  completely.  C.  G.  Hopkins  found  that  on  heating  the 
untreated  oil  in  the  water-oven,  a  small  amount  of  oxygen 
was  absorbed,  the  increase  in  weight  amounting  to  about  I 
per  cent,  at  the  end  of  24  hours. 

The  unsaponifiable  matter  was  high  in  the  samples  exam- 
ined by  Vulte  and  Gibson,  the  phytosterol  being  1.4  percent, 
and  lecithin  about  i.i  per  cent. 

The  most  characteristic  reaction  for  the  oil  is  due  to  the 
phytosterol.  The  oil  is  dissolved  in  carbon  disulfid,  a  drop  of 
strong  sulfuric  acid  added,  and  the  liquid  allowed  to  stand 
for  24  hours.  A  fine  violet  coloration  will  be  produced  with 
maize  oil. 

ARACHIS  OIL 

Arachis  oil — also  called  peanut,  ground-nut,  and  earth-nut 
oil — is  obtained  from  the  seed  of  the  Arachis  hypogcea  L. 
The  cold  expressed  oil  from  the  first  runnings  is  nearly  color- 
less, and  that  of  the  second  expression  usually  of  a  pale 
greenish-yellow.  It  has  an  agreeable  odor  and  flavor,  but  may 
be  obtained  nearly  odorless  and  tasteless.  It  contains  olein, 
palmitin,  stearin,  arachin,  lignocerin,  and  probably  hypogein. 
It  is  used  as  a  salad  oil.  So-called  "peanut  butter"  consists 
simply  of  the  ground  roasted  nuts.  The  principal  use  of  the  oil 
is  as  an  adulterant  for  olive  oil.  The  specific  gravity  and  chemi- 
cal constants  of  the  two  oils  are  so  nearly  alike  that  the  detec- 
tion of  the  admixture  by  these  data  is  hardly  possible.  The 
determination  of  the  iodin  value  is  occasionally  of  use,  but 
16 


FOOD    ANALYSIS 

the  only  reliable  method  is  that  of  Renard,  depending  upon 
the  estimation  of  the  amount  of  arachidic  acid,  or,  more 
properly  speaking,  of  the  arachidic  and  lignoceric  acids,  since 
later  investigation  has  shown  that  the  body  separated  and 
weighed  as  arachidic  acid  consists  of  both,  lignoceric  acid 
being  in  larger  proportion.  The  method  is  laborious,  and 
requires  considerable  care  in  its  performance  ;  many  shorter 
methods  have  been  proposed,  none  of  which  are  as  satis- 
factory as  the  original  method,  which  in  its  most  improved 
form  is  described  by  L.  Archbutt,  as  follows  : 

10  grams  of  the  oil  are  saponified  in  a  deep  porcelain 
basin,  using  8  c.c.  of  aqueous  sodium  hydroxid  solution  (50 
grams  in  100  c.c.)  and  70  c.c.  of  rectified  alcohol.  The 
basin  is  covered,  the  mass  gently  evaporated  to  about  20  c.c., 
rinsed  with  hot  water  into  a  separating  funnel,  decomposed 
with  HC1  in  excess,  and  shaken  with  ether  to  dissolve  the 
fatty  acids.  Two  extractions  with  ether  are  sufficient.  After 
washing  the  ethereal  solution  with  water  it  is  distilled  in  a 
250  c.c.  flask,  the  fatty  acids  dried  by  heating  the  flask  on  a 
steam-bath  and  sucking  out  the  vapor,  and  then  dissolved  in 
the  hot  flask  in  50  c.c.  of  90  per  cent,  alcohol.  The  solution 
must  not  be  allowed  to  cool  below  about  38°.  lest  crystals  of 
lignoceric  or  arachidic  acid  should  separate.  5  c.c.  of  a  20 
per  cent,  aqueous  solution  of  lead  acetate  are  added  and  the 
mixture  cooled  to  about  15°,  shaken,  allowed  to  stand  for 
half  an  hour,  washed  only  once  with  ether,  the  mass  rinsed 
back  into  the  flask  with  a  spray  of  ether,  and  digested  with 
ether  for  a  short  time  ;  then  again  filtered  and  again  rinsed 
back.  After  doing  this  about  four  times,  the  lead  oleate  will 
be  dissolved. 

The  filter  is  opened  in  a  large  plain  funnel  placed  in  the 
neck  of  a  separating  funnel,  and  the  soaps  at  once  rinsed  into 
the  separator  with  a  jet  of  ether.  The  material  that  adheres 
to  the  paper  and  flask  is  decomposed  and  transferred  by  rins- 


ARACHIS    OIL  179 

ing  with  hot  dilute  hydrochloric  acid,  followed  by  ether. 
About  20  c.c.  of  hydrochloric  acid  (i.io  sp.  gr.)  are  poured 
into  the  separator,  shaken  well  to  decompose  the  lead  soaps, 
the  aqueous  liquid  drawn  off",  the  ether  repeatedly  washed 
with  small  quantities  of  cold  water  until  the  lead  chlorid  is 
removed,  distilled  in  a  250  c.c.  flask,  and  the  residual  fatty 
acids  thoroughly  dried  by  heating  on  a  steam-bath.  50  c.c., 
of  ethyl  alcohol  of  exactly  90  per  cent,  strength  (sp.  gr. 
0.834)  are  poured  into  the  flask,  which  is  then  closed  with 
a  cork  carrying  a  thermometer,  heated  cautiously  until  the 
fatty  acids  have  completely  dissolved,  and  cooled  to  15°, 
when  lignoceric  and  arachidic  acids,  if  present,  will  crystal- 
lize out,  either  at  once  or  shortly. 

To  estimate  the  amount,  the  flask  should  be  kept  for  one 
hour,  with  occasional  agitation,  in  a  water-bath  at  either  15° 
or  20°,  or  at  some  intermediate  fixed  temperature  which  is 
nearest  to  that  of  the  laboratory,  the  crystals  collected  on  a 
small  filter,  using  only  the  filtrate  to  rinse  the  flask,  and 
washed  with  three  portions  of  10  c.c.  each  of  90  per  cent, 
alcohol,  at  the  same  fixed  temperature.  A  paper  filter  may 
be  used,  but  a  Gooch  filter,  used  with  gentle  suction,  is 
better,  as  the  mother  liquor  is  more  perfectly  removed  and 
the  washing  more  thorough.  The  filtrate  and  washings  with 
90  per  cent,  alcohol  are  poured  into  a  measuring  cylinder, 
and  the  acids  thoroughly  washed  with  70  per  cent,  alcohol, 
in  which  arachidic  and  lignoceric  acids  are  quite  insoluble, 
until  some  of  the  washings  give  no  precipitate  when  diluted 
with  water.  These  washings  are  thrown  away.  It  is  not 
absolutely  necessary,  but  it  is  advisable  to  redissolve  the  fatty 
acids  thus  obtained  in  50  c.c.  of  90  per  cent,  alcohol,  and 
recrystallize  them,  filtering  and  washing  as  before,  adding  the 
filtrate  and  washings  with  90  per  cent,  alcohol  to  the  first 
quantity  in  the  measuring  clyinder.  Pure  arachidic  and  lig- 
noceric acids  are  thus  obtained,  and  are  dissolved  off  the  filter 


l8o  FOOD    ANALYSIS 

with  boiling  ether,  distilled  down,  and  weighed  in  a  tared 
flask  after  drying  at  100°  for  an  hour.  To  the  weight 
obtained  is  to  be  added  the  amount  dissolved  by  the  90  per 
cent,  alcohol,  which  is  calculated  from  the  following  table, 
based  on  determinations  made  by  Tortelli  and  Ruggeri,  and 
confirmed  by  L.  Archbutt.  It  will  be  noticed  that  the 
4amount  dissolved  varies  according  to  the  weight  of  mixed 
acids  obtained  :  . 

WEIGHT  OF  ARACHIDIC  AND  CORRECTION  PER  100  c.c.  OF  90  PER  CENT. 

LIGNOCERIC  ACIDS  ALCOHOL  USED  FOR  CRYSTALLIZATION 

(Gram).  AND  WASHING  (Gram). 


O.I  or 

0.2 

0.3 
0.4 

0.5 

0.6 
0.7 
0.8 
0.9  an 

(15°  C.) 
less,  0.033 
.  0.048 
0.055 
.    .  0.06  1 

(17-5°  C.) 
0.039 
0.056 
0.064 
0.070 
0.074 
0.077 
0.079 
0.080 
Q.o8l 

(20°  C.) 
O.O46 
O.O64 
0.074 
O.O8O 
0.085 
0.088 
O.O9O 
O.O9I 
O.O9I 

0.064 

0.067 

0.069 
.  o  070 

d  upward,    0.071 

The  proportion  of  arachidic  and  lignoceric  acids  which  has 
been  obtained  by  different  observers  from  arachis  oil  is  very 
fairly  constant,  averaging  about  5  per  cent.,  so  that  the  amount 
of  these  acids  found  in  any  given  mixture  of  oils,  multiplied 
by  20,  will  give  a  close  approximation  to  the  amount  of 
arachis  oil  present. 

SESAME  OIL 

Sesame  oil  (also  called  Gingli  and  Teel  oil)  is  obtained  from 
the  seeds  of  the  Sesamum  orientale  L.  and  S.  indicum  L. 
The  cold  expressed  oil  is  yellow  and  of  pleasant  taste.  It 
consists  of  stearin,  palmitin,  olein,  and  linolin,  with  other  bodies 
not  clearly  understood. 

Sesame  oil  has  been  used  as  a  compulsory  addition  to 
butter-substitutes,  in  order  to  facilitate  the  detection  of  these. 
It  is  readily  recognized  by  the  furfural  test  (page  170). 
Another  test,  devised  by  Tocher,  is  as  follows  : 


RAPE   OIL  l8l 

I  5  c.c.  of  the  oil  are  shaken  in  a  separating  bulb  with  a 
solution  of  i  gram  of  pyrogallol  in  15  c.c.  of  concentrated 
hydrochloric  acid.  The  aqueous  liquid  is  drawn  off  and 
boiled  for  about  five  minutes ;  in  the  presence  of  sesame  oil  it 
becomes  colored,  appearing  red  by  transmitted  and  blue  by 
reflected  light. 

Adulteration. — Sesame  oil  is  liable  to  adulteration,  more 
especially  with  cottonseed,  arachis,  poppyseed,  and  rape  oils. 
These  may  be  detected  as  follows  : 

Cottonseed  oil.  Halphen's,  nitric  acid,  and  Bechi's  tests  ; 
Livache's  test ;  melting-point  of  the  fatty  acids. 

Rape  oil.  Saponification  value  ;  specific  gravity  ;  solidifying 
and  melting  points  of  the  fatty  acids. 

Poppyseed  oil.      lodin  value  ;  temperature  reactions. 

Arachis  oil.  Specific  gravity  ;  determination  of  arachidic 
acid. 

RAPE  OIL 

Rape  oil  is  obtained  from  several  varieties  of  the  Bmssica 
campestris  L.  The  oils  derived  from  all  of  these  are,  as  a  rule, 
described  indiscriminately  as  rape  oil  or  colza  oil ;  but  on  the 
continent  of  Europe  "  colza  oil "  is  sometimes  taken  to  mean 
only  that  from  a  particular  variety  (napus).  The  physical  and 
chemical  characters  of  all  the  varieties  appear  to  be  practically 
identical. 

Rape  oil  is  pale  yellow,  has  a  peculiar  smell,  and  rather  an 
unpleasant  taste.  It  consists  chiefly  of  stearin,  olein,  and 
erucin.  It  also  contains  a  small  proportion  of  arachidin. 
About  0.4  per  cent,  of  arachidic  acid  is  said  to  have  been 
separated  from  it.  It  is  very  liable  to  adulteration,  but  is  of 
interest  here  only  as  an  adulterant  of  olive  oil.  The  physical 
and  chemical  characters  are  given  in  the  tables  on  pages  167 
and  1 68. 


1 82  FOOD    ANALYSIS 

COCONUT  OIL 

Coconut  oil  is  obtained  from  kernels  of  the  coconut, 
especially  Cocos  nucifera  L.  and  C.  butyracea  L.,  being  usu- 
ally expressed  with  aid  of  heat.  It  is  nearly  white  and  about 
the  consistency  of  butter  ;  has  the  taste  and  odor  of  the  coco- 
nut. It  contains  palmitin  and  stearin,  much  myristin  and 
laurin,  with  some  caprin,  caproin,  and  caprylin.  It  gives, 
therefore,  a  notable  amount  of  volatile  acids  and  soluble  acids. 
By  treatment  with  alcohol  and  animal  charcoal,  a  white  neutral 
product  of  agreeable  flavor  and  good  keeping  qualities  is 
obtained,  which  is  sold  for  food  purposes  under  fanciful  names, 
such  as  "  vegetable  butter,"  "  vegetaline,"  "  laureol,"  "  nuco- 
line."  By  submitting  the  oil  to  pressure  products  termed 
"coconut  olein "  and  "coconut  stearin"  are  obtained. 
From  samples  of  these,  A.  H.  Allen  has  obtained  the  follow- 
ing data : 

SP.  GR.  (water  at  15.5°==  i)     SOLIDIFYING-      MELTING-  REICHERT 

AT    15.5°;       AT  98-99°.  POINT.  POINT.         NUMBER. 

Olein, 0.926  0.871  4  rising  to  8       .  5.6 

Stearin, solid  0.869        21.5  rising  1026       28.5  3.1 

CACAO-BUTTER 

Cacao-butter  is  the  fat  expressed  from  cacao  beans.  It  is 
yellowish-white,  becoming  paler  on  keeping,  possesses  the 
pleasant  odor  and  flavor  of  chocolate,  is  solid  at  ordinary 
temperatures,  but  easily  melts  in  the  mouth.  It  consists 
chiefly  of  stearin,  palmitin,  and  laurin,  with  small  proportions 
of  arachidin,  linolin,  formin,  acetin,  and  butyrin.  It  is  insolu- 
ble in  90  per  cent,  alcohol,  but  dissolves  in  5  parts  of  boiling 
absolute  alcohol. 

Adulteration. — The  common  adulterants  of  cacao-butter 
are  tallow,  stearic  acid,  lard,  paraffin  wax,  beeswax,  coconut, 
and  arachis  oils.  The  quantitative  reactions  will  usually  suffice 
for  their  detection. 


CACAO-BUTTER  183 

Stearic  acid  is  indicated  by  the  high  acid  value  ; 

Paraffin  or  beeswax^  by  the  low  saponification  value  and 
high  proportion  of  unsaponifiable  matter  ; 

Vegetable  oils,  by  the  increased  iodin  value  and  lower 
melting-point  of  the  fatty  acids  ; 

Coconut  oil  by  the  low  iodin  value,  high  saponification 
value,  and  moderately  high  Reichert  number. 

The  following  special  tests  are  also  useful  : 

Bjorkland's  Test. — 3  grams  of  the  fat  are  mixed  in  a  test- 
tube  with  6  grams  of  ether,  the  test-tube  closed  with  a  cork, 
and  solution  effected,  if  possible  by  shaking.  When  wax 
is  present,  a  cloudy  liquid  results  which  is  not  changed  on 
warming.  If  the  solution  is  clear,  the  tube  is  placed  in 
melting  ice  and  the  time  observed  after  which  the  solution 
begins  to  become  milky  or  to  deposit  white  flakes  ;  then 
the  temperature  is  noted  at  which  the  mixture  becomes  clear 
on  removing  from  the  ice-water.  Pure  cacao-butter  solution 
becomes  cloudy  in  10  or  15  minutes,  and  becomes  clear  again 
at  19°  to  20°.  With  cacao-butter  containing  5  per  cent,  of 
tallow,  these  figures  are  8  minutes  and  22°  respectively;  10 
per  cent,  of  tallow,  7  minutes  and  25°. 

Filsinger  suggests  a  modified  ether  test :  2  grams  of  the  fat 
are  melted  in  a  graduated  tube  with  6  c.c.  of  a  mixture  of  4 
volumes  of  ether  (sp.  gr.  0.725)  and  2  volumes  of  alcohol 
(sp.  gr.  0.810),  shaken,  and  set  aside.  The  pure  fat  gives  a 
solution  that  remains  clear,  even  on  cooling  to  o°. 

Hager  recommends  the  following  test :  About  I  gram  of 
the  fat  is  warmed  with  2  to  8  grams  of  anilin  until  dissolved  ; 
the  mixture  is  allowed  to  stand  one  hour  at  15°  or  one  and  a 
half  hours  at  17°  to  20°.  Pure  cacao-butter  floats  as  a  liquid 
layer  on  the  anilin.  If  the  sample  contain  tallow,  stearic  acid, 
or  a  little  paraffin,  particles,  which  remain  hanging  on  the 
upper  wall  on  gentle  agitation,  are  formed  in  the  oily  layer. 
If  wax  or  much  paraffin  be  present,  the  layer  solidifies.  If 


184  FOOD    ANALYSIS 

much  stearic  acid  be  present,  layers  will  not  form,  but  the 
whole  will  solidify  to  a  crystalline  mass.  The  oily  layer  from 
pure  cacao-butter  hardens  only  after  many  hours.  A  parallel 
test  should  be  made  with  a  sample  of  known  purity. 


LARD 

Strictly  speaking,  lard  is  the  fat  obtained  from  the  mem- 
branes about  the  kidneys  and  intestines  of  the  common  hog. 
Commercial  lard  consists  of  the  mixed  fat  from  various  parts 
of  the  animal.  The  following  classification  of  American  lard 
is  given  by  H.  W.  Wiley  : 

Neutral  Lard. — Fats  derived  from  the  leaf  in  a  fresh  state. 
The  fat  is  rendered  at  a  temperature  between  40°  and  50°. 
Only  a  part  of  the  lard  is  separated  at  this  temperature.  The 
product  is  almost  neutral,  containing  not  more  than  0.25 
per  cent,  free  acid,  but  it  may  contain  much  water  and  some 
salt. 

Leaf  Lard. — The  residue  unrendered  in  the  above  process 
is  subjected  to  steam  heat  under  pressure. 

Choice  Kettle-rendered  Lard.- — Choice  Lard. — Portions  of  the 
leaf,  together  with  the  fat  cut  from  the  backs,  are  rendered  in 
steam-jacketed  open  kettles.  The  hide  is  removed  from  the 
back-fat  before  rendering. 

Prime  Steam  Lard. — The  whole  head  of  the  hog,  after  the 
removal  of  the  jowl,  is  used  for  rendering.  The  fat  from  the 
small  intestines  and  fat  attached  to  the  heart  are  also  used. 
The  back-fat  and  trimmings  and  the  leaf  may  also  be  used. 
Prime  steam  lard,  therefore,  may  represent  the  fat  of  the  whole 
animal,  or  only  portions. 

A  lower  grade  is  made  from  intestines.  The  definition  of 
the  term  as  u?ed  by  hog-packers  is  :  everything  inside  of  a 
hog  except  the  lungs  and  the  heart,  or,  in  other  words,  the  ab- 
dominal viscera  complete. 


LARD  185 

Lard  consists  of  stearin,  palmitin,  and  olein,  with  a  small 
amount  of  linolin.  O.  Hehner  and  C.  A.  Mitchell  obtained 
stearic  acid  in  proportions  varying  from  6  to  16  per  cent.  It 
contains  but  a  small  amount  of  unsaponifiable  matter ;  Allen 
and  Thomson  found  0.23  per  cent. 

American  and  European  lards  differ  appreciably  in  some 
analytic  characters,  as  exhibited  in  the  following  table  : 


15°'  IODIN  NUMBER. 
American  Lards; 

From  head, 0.8632  65.9 

"     back, 0.8616  63.8 

"     leaf, 0.8626  61.4 

European  Lards  : 

From  back, 0.8607  60.5 

"     kidney, 0.8590  52.6 

"     leaf, 0.8588  53.1 

More  marked  differences  in  the  iodin  value  of  fat  from  dif- 
ferent parts  of  the  animal  have  been  noted  by  other  observers. 

Fresh  lard  usually  contains  little  free  acid,  generally  from 
o.i  to  0.4  per  cent.,  but  the  proportion  may  rise  above  I  per 
cent.  On  exposure  to  the  air  the  amount  increases  consider- 
ably. Spaeth  has  made  a  number  of  determinations  of  free 
acid  of  samples  kept  in  loosely-corked  flasks.  The  following 
is  a  summary  of  the  results  obtained  : 

FRESH.  i  YEAR  OLD.     3  YEARS  OLD. 

Free  acid  calculated  as  oleic,     0.013  to    °-45      °-5l  to    6-°5      2-$  to  J4-2 
Iodin  number, 63.2      1051.7       554    1036.7      41.11021.5 

Adulteration. — Lard  is  much  adulterated,  especially  with 
cottonseed  oil,  cottonseed-stearin,  beef-stearin,  and  excess  of 
water.  Articles  containing  no  lard  have  often  been  sojd 
under  the  name  "  refined  lard."  More  recently  such  prep- 
arations have  been  designated  "lard  compound"  or  "com- 
pound lard."  Maize,  sesame,  and  arachis  oils  may  be  present 
in  these  articles.  Much  attention  has  been  given  to  the  exam- 


1 86  FOOD    ANALYSIS 

ination  of  commercial  lards,  and  the  following  is  a  summary 
of  the  more  trustworthy  of  the  methods.  A  comparison  of 
constants  will  be  found  on  pages  167  and  168. 

Specific  Gravity. — The  specific  gravity  of  lard  is  usually  be- 
tween 0.860  and  0.861.  The  usual  adulterants,  except  beef- 
stearin,  tend  to  raise  the  specific  gravity,  but  they  may  be 
corrected  by  addition  of  vegetable  oils.  J.  H.  Wainwright 
obtained  valuable  data  by  compressing  the  sample  in  muslin 
or  linen  at  ordinary  temperatures  and  examining  the  more 
fluid  portion. 

Melting-point. — This  datum  is  usually  of  little  value.  A. 
Goske  obtained  some  useful  results  by  applying  the  titer-test 
(p.  20).  Pure  lards  gave  figures  ranging  from  23°  to  30°  ; 
lard  adulterated  with  tallow  and  lard  oil,  from  29.7°  to  36°. 
The  solidifying-point  of  the  fatty  acids  may  be  of  value  in 
detecting  maize  oil. 

lodin  Number. — This  differs  considerably  according  to  the 
part  of  the  animal  from  which  the  sample  is  derived.  The 
following  table  has  been  compiled  from  the  results  of  many 
observers  : 

AMERICAN  LARDS. 

Head, 63.     to  85  ;      average,  75. 

Foot,       63.     to  77  ;      average,  70. 

Ham, 66.     1069;      average,  67.8. 

Back,      61.5  to  66.7  ;  average,  64. 1. 

Leaf, 52.51066.7;  average,  59.6. 

Intestines, 60. 

English  lards  may  give  figures  6  or  8  units  lower.     . 

American  steam-lard  derived  from  different  parts  of  the 
animal  has  an  iodin  value  of  about  59  to  66,  but  the  effect  of 
age  on  this  must  not  be  forgotten  (see  page  185).  As  a 
rule,  the  iodin  value  of  mixtures  of  lard,  beef-stearin,  and 
lard  oil  is  well  within  these  limits,  so  that  a  normal  iodin 
value  is  not  proof  of  purity.  The  addition  of  vegetable  oils 
raises  the  figure  notably,  but,  according  to  J.  Lewkowitsch, 


LARD  187 

the  iodin  value  of  the  liquid  fatty  acids  is  the  best  method  of 
detecting  admixture  of  vegetable  fats.  With  American  lard, 
the  figure  is  between  97  and  106;  and  with  European  lards, 
between  90  and  96.  Should  a  sample  give  a  value  within  the 
above  limits,  it  must  be  further  examined  for  beef-stearin  and 
coconut  oil,  since  these  may  be  added  with  a  vegetable  oil  to 
bring  the  figure  within  the  limits  of  normal  lard. 

Thermal  Test. — The  rise  of  temperature  with  sulfuric  acid, 
and  more  especially  the  heat  of  bromination,  is  of  service 
in  the  detection  of  cottonseed  products.  The  results  with 
Maumene's  test,  as  reported,  differ  greatly.  It  is  advisable 
to  perform  tests  with  samples  of  pure  lard  and  cottonseed 
oil  side  by  side  with  the  suspected  sample.  The  initial  tem- 
perature may  be  about  35°  or  40°.  Care  should  be  taken 
that  the  sample  contains  no  water. 

Refractometric  Examination. — The  examination  of  lard  by 
the  oleorefractometer  or  the  butyrorefractometer  is  of  value. 
Vegetable  oils  are  readily  detected,  but  the  indications  in 
the  case  of  beef  tallow  and  stearin  are  not  so  satisfactory. 
According  to  F.  Jean,  better  results  are  obtained  by  operating 
on  the  liquid  fatty  acids.  The  following  table  is  compiled 
from  the  results  of  Jean,  Dupont,  and  other  observers.  The 
liquid  fatty  acids  may  be  prepared  as  described  on  page  144. 
Jean,  whose  figures  are  given  in  the  table,  prepares  them  by 
Sear's  process  :  50  grams  of  the  lard  are  saponified,  the 
fatty  acids  separated  by  addition  of  acid,  washed  with  hot 
water,  and  mixed  in  a  flask  together  with  250  c.c.  of  carbon 
disulfid  and  8  to  10  grams  of  zinc  oxid.  The  zinc  salts  of 
the  liquid  fatty  acids  dissolve  in  the  carbon  disulfid,  and  can 
thus  be  separated  from  the  solid  fatty  acids.  The  carbon 
disulfid  is  evaporated,  the  fatty  acids  liberated  with  hydro- 
chloric acid,  well  washed  with  hot  water,  and  dried  at  a  tem- 
perature of  120°. 


i88 


FOOD    ANALYSIS 


DEGREES  IN  OLEOREFRACTOMETER. 
Fat. 


Liquid  Fatty 
Acids. 


American  lard,  mixed, —  7 

"  "     leaf, —  1 1. 5 

"  "     foot,  back,  head,  etc., — 4  to — n 

European    "      —  12  to —  13      —  30 

"  "     stearin, —  10  to — II 

Beef  tallow, ...  —  i6to —  17      —  40 

"    stearin, , —  34 

Veal       "  —  19 

Coconut  oil, —  54 

Cottonseed  oil, -j-  12  to  -)-  23 

usually  -f  20  -f-  10 

"          stearin, -f-  25  -f~  2O 

Arachis  oil, -j-  3.5  to  -{-  7  —  15 

Sesame  "        -j-  13  to  -f  18  —  18 

European  lard  with  20  per  cent,  cottonseed  oil,    ...  —  6 

10  "  stearin,     .  —  7 

30  «  «  .  —  3 

50  "  «._|_i 

20  sesame  oil, —  20 

20  arachis  " —  8  —  23 

50  beef  tallow,     ....  —  14  —  33 

40  ;  beef  fat,  40  ;  cottonseed  oil,  20  per 

cent.,       —  24 

European  lard  60 ;  mutton  tallow,  25  ;  arachis  oil,  15 

per  cent. , —  13  —  22 

European  steam  lard,  60 ;  beef  tallow,  15  ;  arachis  oil, 

25  per  cent., —  8 

SPECIAL  TESTS. 

Seed  Oils  (cottonseed,  sesame,  arachis,  and  maize)  ;  iodin 
number  of  the  liquid  fatty  acids.  These  are  further  specifically 
identified  as  follows : 

Cottonseed  Oil. — Lard  from  animals  fed  liberally  on  cotton- 
seed products  may  give  faint  reactions  for  cottonseed-  oil  by 
the  qualitative  tests.  Halphen's  test  is  the  most  satisfactory. 
The  nitric  acid  and  Bechi's  tests  may  also  be  applied.  Pure  lard 
that  has  been  exposed  to  the  air  may  respond  to  Bechi's  test, 
so  that  the  sample  should  be  carefully  taken  from  the  interior 
of  the  mass.  On  the  other  hand,  cottonseed  oil  that  has  been 
heated  for  a  short  time  to  240°  no  longer  responds  to  this 
test,  and  reacts  to  Halphen's  test  with  diminished  intensity. 


LARD 


189 


B.  W.  Jones  suggested  sulfur  chloric!  as  a  test  for  cottonseed 
oil,  which  forms  with  it  a  hard  mass  partly  insoluble  in  carbon 
disulfid.  J.  Lewkowitsch  has  found  the  method  useful,  and 
applies  it  as  follows  :  5  grams  of  the  fat  are  dissolved  in  2  c.c. 
of  carbon  disulfid,  2  c.c.  of  sulfur  chlorid  are  added,  and  the 
mixture  heated  on  the  water-bath.  The  following  results  were 
obtained  with  mixtures  of  lard  and  cottonseed  oil  : 


COTTONSEED  OIL  PER- 
CENTAGE. 

None,      .    .    .    . 
10  .....*. 

20 

30 

40 

50 Solid  after 

60 

70 

80 

90 

100 


.  No  reaction. 

.  Thickens  after  35  minutes. 

"          "30 

"          "     26 

"          "     18 

10  minutes. 


SOLUBILITY  OF  PRODUCT 
IN  CARBON  DISULFID. 

Completely  soluble. 
«  « 

52.0  per  cent,  soluble. 
39.6       " 
34-8       " 

37.4  per  cent,  soluble. 

30.6       " 

32.6       " 

30.0       "  " 

24.0       " 


It  is  recommended  to  test  the  sample  side  by  side  with  pure 
lard,  or  with  mixtures  of  known  composition. 

Cottonseed  Stearin. — For  the  detection  of  this  the  above 
tests  for  cottonseed  oil  should  be  applied,  also  specific  gravity 
determination. 

Arachis  OIL — Renard's  test  should  be  applied  (page  178). 

Sesame  Oil. — Baudouin's  test  should  be  applied  (page  170). 

Maize  Oil. — In  the  absence  of  other  seed  oils,  the  melting- 
point  of  the  mixed  fatty  acids  is  of  use. 

Coconut  Oil. — The  iodin  number,  saponification  value,  and 
Reichert  number  are  useful  data. 

Talloiv. — Beef-stearin. — Belfield  proposed  to  use  the  follow- 
ing :  The  sample  is  dissolved  in  warm  ether  and  the  solution 
is  cooled  slowly  and  the  crystals  deposited  are  examined  under 
the  microscope.  Crystallization  should  take  place  as  slowly 
as  possible.  A  good  method  is  to  place  a  cotton  plug  in  the 
mouth  of  the  tube,  and  allow  the  ether  to  evaporate  slowly. 


FOOD    ANALYSIS 

The  crystals  from  pure  lard  are  usually  in  the  form  of  plates 
with  oblique  terminals. 

C.  B.  Cochran  2  2  finds  the  following  method  satisfactory  : 
2  c.c.  of  the  melted  fat  are  mixed  with  22  c.c.  of  fusel  oil 
and  the  mixture  warmed  to  about  blood  heat,  and  when  com- 
plete solution  is  effected  it  is  allowed  to  cool  slowly  to  16°  or 
17°  and  maintained  at  this  temperature  for  several  hours,  dur- 
ing which  a  crystalline  deposit  forms.  This  is  transferred  to 
a  filter,  the  fusel  oil  drained  off  as  far  as  possible,  and  a  part 
or  whole  of  the  residue  dissolved  in  ether  in  a  test-tube,  the 
mouth  of  the  tube  being  plugged  with  cotton.  The  crystals 
which  form  on  standing  may  be  mounted  in  cottonseed  oil 
and  examined  under  the  microscope. 

The  proportion  of  beef-stearin  present  may  be  approxi- 
mately estimated  by  W.  F.  K.  Stock's  modification  of  Bel- 
field's  test.  It  consists  in  comparing  the  crystals  obtained 
from  an  ethereal  solution  with  those  from  two  standard  sets 
of  mixtures,  the  first  consisting  of  pure  lard  melting  at  34°  to 
35°,  with  5,  10,  15,  and  20  per  cent,  of  beef-stearin  melting 
at  56°;  the  second  of  pure  lard,  of  melting-point  of  39°  to 
40°,  with  5,  10,  15,  and  20  per  cent,  of  beef-stearin  melting 
at  50°.  The  process  is  as  follows  :  The  melting-point  of  the 
sample  is  determined  by  the  capillary  tube  method.  Suppose 
the  melting-point  be  found  at  34°,  3  c.c.  of  the  melted  fat  are 
run  into  a  graduated  cylinder  of  about  25  c.c.  capacity;  21 
c.c.  of  ether  are  added,  and  the  fat  dissolved  at  20°  to  25°  ;  3 
c.c.  of  each  of  the  first  set  of  mixtures  are  treated  in  exactly 
the  same  way.  The  five  cylinders  are  cooled  down  to  13°, 
and  allowed  to  remain  at  that  temperature  for  24  hours.  An 
approximate  estimate  as  to  the  amount  of  the  adulterant  is 
arrived  at  by  reading  off  the  apparent  volume  of  the  deposited 
crystals.  The  ether  is  then  poured  off  as  far  as  possible,  and 
10  c.c.  of  fresh  ether  at  13°  are  added  in  each  case.  The  cyl- 
inders are  again  shaken,  cooled  as  before,  and  the  proportion 


BUTTER-FAT  IQI 

of  crystals  read  off  as  before.  Finally,  the  contents  are 
emptied  into  weighed  shallow  beakers,  the  ether  drained  off 
carefully,  the  mass  allowed  to  dry  for  15  minutes  at  ioo°,and 
weighed.  The  weight  obtained  for  the  sample  under  exami- 
nation is  compared  with  the  weight  of  the  crystals  obtained 
from  the  standard  nearest  to  it.  The  second  set  of  mixtures 
is  used  for  samples  of  higher  melting-point.  The  actual 
presence  of  beef-fat  must  be  proved  by  microscopic  examina- 
tion, when  the  characteristic  tufts  are  seen.  No  sample  of 
pure  lard  melting  below  39°  yielded  more  than  o.on  gram 
of  crystals  under  the  above  conditions.  A  sample  of  the 
melting-point  45.8°  gave,  however,  0.146  gram  of  crystals. 

Beef-fat  crystallizing  from  ether  forms  spherical  masses, 
which  when  pressed  under  a  cover-glass  become  fan-shaped 
tufts.  Under  high  magnification  the  individual  crystals  still 
appear  in  needle-like  form  quite  distinct  from  the  plates  pro- 
duced by  lard.  In  samples  of  lard  containing  beef-fat  the 
crystals  obtained  are  not  a  mixture  of  those  typical  of  the 
two  substances,  but  usually  uniform  and  resemble  those  of 
lard  somewhat  modified.  In  some'  cases  the  manner  of 
aggregation  is  similar  to  that  of  beef-fat  crystals,  but  the 
individual  crystals,  instead  of  being  needle-shaped,  have  more 
the  appearance  of  those  from  lard.  It  will  often  be  necessary 
to  recrystallize  repeatedly  under  varying  conditions,  to  get 
characteristic  crystals. 


BUTTER-FAT 

The  fat  of  cow's  milk  is  the  only  one  of  importance,  and 
this  is  only  known  commercially  in  the  form  of  butter,  a 
mixture  of  the  fat  with  varying  proportions  of  water,  salt,  curd, 
coloring-matter,  sometimes  boric  acid,  and  other  fats.  For 
methods  of  analysis  and  distinction  of  butter-fat  from  other 
fats,  see  under  "  Milk  Products." 


FOOD    ANALYSIS 


MILK  AND    MILK   PRODUCTS 

Milk,  the  nutritive  secretion  of  nursing  mammals,  consists 
of  water,  fat,  proteids,  sugar,  and  mineral  matters.  Cow's 
milk  is  meant  in  all  cases,  unless  otherwise  stated. 

The  chemistry  of  milk  formation  is  not  entirely  understood. 

Fat.  —  This  occurs  in  globules  varying  from  0.0015  mm.  to 
0.005  mm-  m  diameter,  in  a  condition  which  prevents  spon- 
taneous coalescence.  This  property  has  been  regarded  as 
indicating  a  surrounding  membrane,  but  may  be  explained 
without  such  an  assumption. 

According  to  V.  Storch,  each  globule  of  milk  is  coated  with 
a  membrane  of  mucoid  substance.  These  membranes  or  semi- 
fluid envelopes  are  retained  when  the  fat  globules  are  washed 
free  from  milk  serum  ;  they  may  be  stained  and  seen  under 
the  microscope. 

The  fat  of  milk  is  peculiar  among  animal  fats  in  containing 
a  notable  proportion  of  acid  radicles  with  a  small  number  of 
carbon  atoms. 

Proteids.  —  The  nature  of  the  proteids  of  milk  has  been  much 
discussed,  but  it  is  now  generally  conceded  that  there  are  at 
least  three  forms,  casein,  albumin,  and  globulin,  the  casein 
being  present  in  by  far  the  greatest  amount,  and  the  globulin  as 
traces  only.  V.  Storch  found  a  fourth  proteid,  which  he  re- 
gards as  an  envelope  surrounding  the  fat  globules,  but  H.  D. 
Richmond,  while  confirming  the  existence  of  this  body,  doubts 
that  it  is  connected  with  the  fat 

CASEIN.  —  Casein  is,  in  part,  at  least,  probably  in  combination 
with  phosphates.  It  is  precipitated  by  acids,  rennet,  magnesium 
sulfate,  and  many  other  substances.  Acids  precipitate  it  by 
breaking  up  the  combination  with  phosphates.  The  action  of 
rennet  is  more  complex.  Hammersten's  investigations  indicate 
that  it  is  dependent  upon  the  presence  of  calcium  salts  ;  thus, 
if  the  curd  precipitated  by  dilute  acid  be  dissolved  in  dilute 


MILK  AND  MILK  PRODUCTS  193 

alkali  and  the  solution  neutralized,  it  is  unaffected  by  rennet, 
but  regains  its  coagulability  by  the  addition  of  a  solution  of  a 
calcium  salt  or,  what  amounts  to  the  same  thing,  a  little  of  the 
whey  from  which  the  casein  was  precipitated.  It  appears  that 
rennet  splits  the  casein  into  two  proteids,  one  of  which  is 
precipitated  in  the  curd. 

The  results  of  some  experiments  made  by  Bardach  indicate 
that  the  coagulation  of  milk  on  heating  is -due  to  the  alteration 
of  the  casein  into  such  a  state  that  it  can  be  precipitated  by  the 
small  amount  of  acid  derived  from  the  lactose,  which  is  other- 
wise incapable  of  affecting  it. 

Films  of  proteid  matter  occur  abundantly  in  milk,  for  which 
reason  it  is  distinctly  opaque,  even  when  all  but  a  trace  of  the 
fat  has  been  removed  by  centrifugal  action. 

The  albumin  of  milk  appears  to  be  a  distinct  form,  and  is 
called  lactalbumin.  It  is  not  precipitated  by  dilute  acids,  but 
is  coagulated  by  heating  to  7O°-75°.  The  proportion  in 
cow's  milk  is  usually  from  0.35  to  0.50  per  cent.,  but  colos- 
trum may  contain  much  larger  proportions. 

Globulin  is  present  only  in  minute  amounts  in  normal  milk, 
but  colostrum  may  contain  as  much  as  8  per  cent.  It  is 
coagulated  on  heating. 

Lactose. — This  is  peculiar  to  milk.  Richmond  discovered 
in  the  milk  of  the  gamoose  a  sugar  not  identical  with  lactose. 

Citric  acid  is  a  normal  constituent  of  the  milk  of  various 
animals.  In  human  milk,  the  quantity  is  about  0.5  gram  to 
the  liter;  in  cow's  milk,  from  I  to  1.5  grams.  It  is  not  de- 
pendent on  the  citric  acid  present  in  the  food. 

Minute  amounts  of  nitrogenous  bases  and  a  starch -liquefying 
enzym  also  occur. 

Mineral  Matter. — The  ash  of  milk  contains  calcium,  mag- 
nesium, iron,  potassium,  and  sodium  as  chlorids,  carbonates, 
sulfates,  and  phosphates.  It  does  not  correctly  represent  the 
salts  present  in  milk.  On  ignition  of  the  organic  salts,  car- 
17 


194  FOOD    ANALYSIS 

bonates  are  formed,  which  in  turn  are  decomposed  by  the 
phosphoric  acid  formed  by  the  oxidation  of  the  phosphorus 
of  the  casein. 

H.  D.  Richmond  has  determined  the  ratio  of  the  ash  to  the 
solids  not  fat  of  135  samples  of  milk.  This  was  found  to 
range  from  7.8  to  9.4  per  cent.,  but  more  usually  from  7.8  to 
8.5  (average  8.2)  per  cent.  A  considerable  proportion  were 
found  to  be  alkaline  to  turmeric,  litmus,  and  phenolphthalein, 
the  maximum  alkalinity  being  0.025  per  cent.,  calculated  as 
sodium  carbonate. 

The  following  table  gives  the  general  composition  of  some 
milks.  Analyses  of  the  milk  of  less  important  animals  have 
been  published,  but  the  figures  are  of  uncertain  value,  because 
it  is  not  sure  that  the  samples  were  of  average  character  or  the 
methods  of  analysis  accurate  : 

HUMAN.        Cow.         MARE.         GOAT.  Ass.       GAMOOSE. 


Fat  

.       7.7 

4.O 

i.i 

4.7 

1.6 

5.6 

Sugar, 
Proteids,    .    .    . 
Ash,  

.    .    .    6.8 

.  ::'.    1.8 

.     .     .     0.2 

Is 

3-5 
0.7 

6.7 
1.9 

°-3 

4.0 

4.6 
0.6 

6.1 

2.2 

o-5 

5-4 

3-8 

I.O 

12. 1  Ij.O  10.0  13.5  10.4  15.8 

Normal  milk  is  an  opaque  white  or  yellowish-white  fluid, 
with  an  odor  recalling  that  of  the  animal,  and  a  faint  sweet 
taste.  The  opacity  is  due  largely  to  the  fat  globules,  but  when 
these  are  entirely  removed  the  liquid  does  not  become  trans- 
parent. The  reaction  of  freshly  drawn  milk  to  litmus  is 
usually  alkaline,  but  is  sometimes  amphoteric  ;  that  is,  it  turns 
the  red  paper  blue  and  the  blue  paper  red.  The  specific 
gravity  varies  between  1.028  and  1.035.  It  usually  undergoes 
a  gradual  augmentation  (sometimes  termed  Recknagel's  phe- 
nomenon) for  a  considerable  time  after  the  sample  has  been 
drawn.  The  increase  may  amount  to  two  units  (water  being 
i.ooo).  The  specific  gravity  becomes  stationary  in  about  5 
hours  if  the  milk  be  maintained  at  a  temperature  below  15°, 


MILK    AND    MILK    PRODUCTS 

but  at  a  higher  temperature  it  may  require  24  hours  to  acquire 
constancy.  The  change  is  not  dependent  on  the  escape  of 
gases,  and  is  believed  to  be  due  to  some  molecular  modifica- 
tion of  the  casein,  possibly  under  the  influence  of  an  enzym. 

Unless  collected  with  special  care  and  under  conditions  of 
extreme  cleanliness,  milk  always  contains  bacteria  and  animal 
matter  of  an  offensive  character,  such  as  epithelium,  blood  and 
pus  cells,  particles  of  feces,  and  soil. 

At  ordinary  temperature  milk  soon  undergoes  decomposition, 
by  which  the  milk-sugar  is  converted  principally  into  lactic  acid, 
and  the  proteids  partly  decomposed  and  partly  coagulated. 
The  liquid  becomes  sour  and  the  fat  is  inclosed  in  the  coagu- 
lated casein. 

In  the  initial  stages  of  decomposition  the  proteids  frequently 
undergo  transformations  into  substances  which  are  the  cause 
of  the  violent  poisonous  effects  occasionally  produced  by  ice- 
cream and  other  articles  of  food  into  the  preparation  of  which 
milk  enters. 

Boiling  produces  coagulation  of  the  albumin,  some  caramel- 
ization  of  the  sugar,  and  develops  a  greater  facility  of  coales- 
cence on  the  part  of  the  fat  globules.  Enzyms  and  most 
microbes  are  destroyed.  The  skin  which  forms  on  the 
surface  of  boiling  milk  is  composed  largely  of  casein.  It 
is  due  probably  to  the  more  rapid  evaporation  at  the  surface 
of  the  liquid. 

When  milk  is  allowed  to  stand,  some  of  the  fat  rises 
gradually  and  forms  a  rich  layer,  constituting  cream.  The 
proportion  of  cream  depends  on  several  conditions.  The 
amount  formed  in  a  given  time  cannot  be  taken  as  a  measure 
of  the  richness  of  the  milk.  Water  added  to  milk  causes  a 
more  rapid  separation  of  the  cream. 

When  milk  is  subjected  to  centrifugal  action,  a  larger  pro- 
portion of  cream  is  quickly  obtained,  nearly  all  of  the  fat  being 


196  FOOD    ANALYSIS 

removed.     The     following     figures,    given     by    D'Hout     as 
averages,  show  the  effect  of  the  centrifugal  action  : 

WHOLE  MILK.    SEPARATED  MILK.         CREAM. 

Specific  gravity,    .    .    .  1032  1034  1015 

Total  solids,      .    .    .    .14.10  9.6  26.98 

Sugar, 4.70  5.05  3.32 

Casein, 3.50  3.62  2.02 

Ash, 0.79  0.78  0.58 

Fat 5.05  0.20  21.95 

Buttermilk  is  the  residue  after  removal  of  the  butter  by 
churning.  P.  Vieth  gives  the  following  analyses  : 

TOTAL  SOLIDS.  FAT.  SOLIDS  NOT  FAT.  ASH. 

9.03  0.63  8.40  0.70 

8.02  0.65  7.37  1.29 

10.70  0.54  10. 16  0.82 

The  whey  left  after  the  precipitation  of  the  curd  by  rennet 
or  acid  still  contains  a  notable  amount  of  proteids.  The 
following  analyses  are  by  C.  B.  Cochran  : 

MILK.  WHEY. 

Total  solids.  Solids  not  fat.                       Total  solids.        Proteids  removed. 

9.27  9.13  6.62  2.51 

9.27  9.13  6.1  3.03 

I4-05  8.35  6.62  2.33 

7.71  7.61  5.98  1.63 

8.91  8.71  6.50  2.21 

The  whey  of  any  given  milk  has  the  same  composition, 
whether  taken  from  the  original  milk,  skimmed  milk,  or  cream. 

Average  Proportion  of  Solids  in  Milk. — The  most  extensive 
data  on  this  point  are  those  obtained  by  P.  Vieth.  The  total 
number  of  samples  was  120,540.  The  averages  of  the  entire 
series  are  as  follows^: 

Fat, ' .    4. 1  per  cent 

Non-fatty  solids, 8.8       " 

Total  solids, 129       " 

H.  D.  Richmond's  results  for  several  years  have  confirmed 
these  figures. 


MILK   AND    MILK    PRODUCTS  I 97 

Seasonal  Variations  in  the  Composition  of  Milk. — Victh's 
results  show  that  poorest  quality  occurs  during  the  first  half 
of  the  year,  especially  in  April.  A  low  figure  is  also  fre- 
quently noted  about  July.  In  autumn  the  quality  rises,  being 
highest  in  October  and  November. 

Deficient  Solids. — The  following  are  some  instances  of 
deficiency  of  solids  in  milk  known  to  be  genuine  : 

TOTAL 
SP.  GR.         FAT.       S.  N.  F.        SOLIDS.  ANALYST. 


1029.6  3.38  7.95  H-33  C.  B.  Cochran 

1030.0  3.62  8.31  H-93  C.  B.  Cochran 

1029.3  3.63  8.02  11.65  c-  B-  Cochran 

...  3.99  8.36  12.35  Leffmann  and  Beam 

.    .    .  3.11  8.33  11.441  Monthly   Averages 

.    .    .  3.05  8.33  11.38  [•          N.  J.  State  Agricul- 

.    .    .  3.23  8.44  11-67]  tural  Exp.  Station. 


The  following  analyses  of  milk  from  individual  cows  were 
made  by  C.  B.  Cochran.  The  samples  were  taken  under  pre- 
cautions which  insured  their  genuineness.  The  data  are  all 
direct  determinations.  The  total  solids  were  obtained  by 
drying  in  the  usual  manner,  and  the  fat  by  the  L-B.  method. 
Low  milks  have  been  often  noted  in  the  vicinity  of  Phila- 
delphia. 

SP.  GR. 

1026.6 
1028.8 
1028.8 
1033-5 

In  a  herd  of  60  cows,  H.  D.  Richmond  found  19  per  cent, 
of  the  samples  to  contain  between  8.38  and  8.50  per  cent, 
solids  not  fat.  From  an  examination  of  the  records  of 
analyses  made  in  the  laboratory  of  the  Aylesbury  Dairy 
Company  for  many  years  past  Richmond  finds  that  the  milks 
believed  to  be  genuine  which  contained  less  than  8.3  per  cent, 
of  solids  not  fat  numbered  59  per  100,000;  and  those  with 
less  than  8.1  per  cent.,  10  per  100,000.  Such  results  are 


FAT. 

S.  N.  F. 

TOTAL  SOLIDS. 

2-35 

6.78 

9-13 

2-95 

7.56 

10.51 

2.40 

7.56 

9.96 

2.90 

8.68 

11.58 

198  FOOD    ANALYSIS 

only  obtained  with  milk  of  individual  cows.  The  mixed  milk 
from  a  herd  of  any  considerable  number  will  rarely,  if  ever, 
show  a  proportion  of  non-fatty  solids  less  than  8.5  per  cent, 
nor  less  than  3.5  per  cent  of  fat.  Cochran  examined  the 
milk  from  each  cow  of  a  herd  of  59,  with  the  following 
results  : 

Fat, 2.60  to   5.40 

Total  solids, 9.861013.78 

The  average  milk  of  the  entire  herd  was  : 

Fat, 3. 76  per  cent. 

Total  solids, 12.33  per  cent. 

The  average  of  nearly  100  determinations  at  the  University 
of  Wisconsin  creamery  during  a  protracted  drought  in  1895 
gave  but  a  trifle  over  8.5  per  cent,  solids  not  fat.  The  casein 
was  low  in  this  milk,  while  the  sugar  was  about  normal  in 
amount.  Similar  conditions  have  been  observed  by  L.  L. 
Van  Slyke  at  the  New  York  Station. 

Colostrum. — This  is  the  secretion  in  the  early  stages  of 
lactation,  and  differs  from  ordinary  milk.  It  contains  char- 
acteristic structures,  known  as  colostrum  corpuscles,  and 
usually  contains  much  less  fat  than  fully  developed  milk,  but 
a  larger  proportion  of  proteids.  Colostrum  coagulates  on 
boiling.  Lactose  is  in  small  amount. 

Analytic  Processes. 

As  already  noted,  the  specific  gravity  of  milk  rises 
gradually  for  some  time  after  it  has  been  drawn,  and  the 
determination  is  to  be  made  only  after  this  action  has  ceased. 
This  will  require  about  5  hours  after  the  milk  is  drawn,  if  it 
has  been  kept  below  15°,  but  at  a  higher  temperature  it 
will  be  necessary  to  allow  at  least  12  hours.  For  all  other 
determinations  the  milk  must  be  analyzed  as  soon  as  possible. 
The  following  figures,  published  by  Bevan,  show  that  a  con- 
siderable loss  in  total  solids  may  occur  in  24  hours  : 


MILK  AND  MILK  PRODUCTS  199 

TOTAL  SOLIDS.  Loss. 

Evaporated  immediately, IJ-73 

Evaporated  after    24  hours, 10.79  0.94 

Evaporated  after    48  hours, 10.38  1.35 

Evaporated  after  1 20  hours, 9.42  2.31 

The  decomposition  is  very  irregular,  and  it  is  not  possible 
to  determine,  by  estimation  of  the  lactic  acid  or  other 
products,  the  original  composition  of  the  milk.  The  pipet 
used  for  taking  a  portion  for  analysis  should  have  a  wide 
opening,  that  no  cream  may  be  retained  when  the  pipet  is  dis- 
charged. 

When  rigid  accuracy  is  not  essential,  it  will  suffice  to 
measure  the  portion  of  milk  taken  for  the  determinations. 
P.  Vieth  uses  a  pipet  graduated  to  deliver  5  grams,  and  finds 
that,  working  with  whole  and  skimmed  milk,  under  the 
ordinary  variations  of  temperature,  the  error  will  not  exceed 
o.  I.  on  the  total  solids  and  is  less  on  the  fat. 

A  good  plan  is  to  use  a  5  c.c.  pipet  and  to  wash  out  that 
which  adheres  to  the  glass  with  a  little  water.  The  specific 
gravity  of  the  milk  being  known,  the  amount  taken  can  be 
calculated.  The  milk  should  be  as  near  15.5°  as  possible. 

Specific  Gravity. — Air-bubbles  are  held  rather  tenaciously 
by  milk,  and  care  must  be  taken  in  mixing,  preparatory  to 
taking  the  specific  gravity,  to  avoid  as  far  as  possible  the  in- 
closure  of  air,  and  to  allow  sufficient  time  for  the  escape  of 
any  bubbles  that  may  be  present.  The  specific  gravity  of 
milk  is  understood  to  be  taken  at  15.5°  ;  samples  should  be 
brought  near  to  this.  If  at  a  few  degrees  above  or  below,  it 
will  suffice  to  make  the  determination  at  once  and  obtain  the 
correct  figure  by  reference  to  the  annexed  table.  The  spe- 
cific gravity  of  normal  milk  varies  between  1.028  and  1.035. 
The  figure  alone  does  not  indicate  the  character  of  the  sample, 
but  taken  in  conjunction  with  the  figure  for  fat  or  for  total 
solids,  it  is  of  value  as  a  check  on  the  results  furnished  by 
other  determinations. 


2OO 


FOOD    ANALYSIS 


The  simplest  method  of  determining  specific  gravity  is  by 
the  lactodensimeter,  a  delicate  and  accurately  graduated  hydro- 
meter. The  instrument  must  be  immersed  carefully  so  as  not 
to  wet  the  stem  above  the  point  at  which  it  will  rest.  The 
instrument  should  be  tested  by  immersion  in  distilled  water 
at  15.5°  and  milks  of  known' specific  gravity. 

The  indications  furnished  by  the  lactodensimeter  are  suffi- 
ciently accurate  for  most  purposes,  but  its  employment  neces- 
sitates a  considerable  amount  of  the  sample. 


Find  the  temperature  of  the  milk  in  one  of  the  horizontal  lines  and  the  specific 
gravity  in  the  first  vertical  column.  In  the  same  line  with  this  and  the  tempera- 
'ture  the  corrected  specific  gravity  is  given. 


°F.|  50 

51 

52 

53 

54 

55 

56 

57 

58 

59 

60 

61 

62 

•MM 
SP. 

GR. 

21 

^^^—> 

20.2 

20.3 

20.3 

20.4 

20.5 

20.6 

20.7 

20.8 

20.9 

20.9 

21.0 

21.  1 

21.2 

22 

21.2 

21.3 

21-3 

21.4 

21-5 

21.6 

21.7 

21.8 

21.9 

21.9 

22.0 

22.1 

22.2 

23 

22.2 

22.3 

22.3 

22.4 

22.5 

22.6 

22.7 

22.8 

22.8 

22.9 

23.0 

23.1 

23.2 

24 

23.2 

23-3 

23-3 

23-4 

23-5 

23.6 

23.6 

23-7 

23.8 

23-9 

24.0 

24.1 

24.2 

25 

24.1 

24.2 

24-3 

24.4 

24-5 

24.6 

24.6 

24.7 

24.8 

24.9 

25.0 

25.1 

25.2 

26 

25-1 

25.2 

25.2 

25-3 

25-4 

25-5 

25.6 

25.7 

25.8 

25-9 

26.0 

26.1 

26.2 

27 

26.1 

26.2 

26.2 

26.3 

26.4 

26.5 

26.6 

26.7 

26.8 

26.9 

27.0 

27.1 

27-3 

28 

27.0 

27.1 

27.2 

27-3 

27.4 

27-5 

27.6 

27.7 

27.8 

27.9 

28.0 

28.1 

28.3 

29 

28.0 

28.1 

28.2 

28.3 

28.4 

28.5 

28.6 

28.7 

28.8 

28.9 

29.0 

29.1 

29-3 

30 

29.0 

29.1 

29.1 

29.2 

29-3 

29.4 

29.6 

29.7 

29.8 

29.9 

30.0 

3O.I 

30-3 

31 

29.9 

30.0 

3O.I 

30.2 

30-3 

30-4 

30-5 

30.6 

30.8 

3°-9 

3I.O 

31.2 

31.3 

32 

30.9 

31.0 

31-1 

31.2 

3*-3 

31.4 

3i-5 

31.6 

31-7 

3i-9 

32.0 

32.2 

32-3 

33 

31-8 

31-9 

32.0 

32.1 

32-3 

32.4 

32-5 

32.6 

32.7 

32.9 

33-° 

33-2 

33-3 

34 

32.7 

32.9 

33-o 

33-i 

33-2 

33-3 

33-5 

33.6 

33-7 

33-9 

34-o 

34-2 

34-3 

35 

33-6 

33-8 

33-9 

34-o 

34-2 

34-3 

34-5 

34-6 

34-7 

34-9 

35-o 

35-2 

35-3 

°C. 

10 

i^mm^^m 

10.5 

ii.  i 

n.6 

12.2 

12.7 

13-3 

13-8 

14.4 

*S-° 

15-5 

16.1 

16.6 

MILK    AND    MILK    PRODUCTS 


201 


More  accurate  determination  can  be  made  by  the  methods 
detailed  in  the  introductory  part  (page  41),  the  most  suitable 
being  the  Sprengel  tube.  According  to  H.  D.  Richmond,  the 
pyknometer  is  less  suitable  for  rigidly  accurate  work,  on  ac- 
count of  the  tendency  of  the  cream  to  separate  before  the 
mass  has  acquired  the  standard  temperature. 

Total  Solids. — This  determination  may  often  be  made 
with  sufficient  accuracy  for  practical  purposes  by  evaporating 
a  measured  volume  (e.  g.,  3  or  5  c.c.)  in  a  shallow  nickel 


63 

64 

65 

66 

67 

68 

—  —  —  — 

69 

—  — 

70 

71 

72 

.z^aaH 

73 

74 

75 

21.3 

21.4 

21-5 

21.6 

21.7 

21.8 

22.0 

22.1 

22.2 

22.3 

22.4 

22.5 

22.6 

22.3 

22.4 

22.5 

22.6 

22.7 

22.8 

23.0 

23.1 

23-2 

23-3 

23.4 

23-5 

23-7 

23-3 

23-4 

23-5 

23.6 

23-7 

23-8 

24.0 

24.1 

24.2 

24-3 

24.4 

24.6 

24.7 

24-3 

24.4 

24-5 

24.6 

24.7 

24.9 

25.0 

25-1 

25.2 

25-3 

25-5 

25.6 

25-7 

25-3 

25-4 

25-5 

25.6 

25-7 

25-9 

26.O 

26.1 

26.2 

26.4 

26.5 

26.6 

26.8 

26.3 

26.5 

26.6 

26.7 

26.8 

27.0 

27.1 

27.2 

27-3 

27.4 

27.5 

27.7 

27.8 

27.4 

27-5 

27.6 

27.7 

27.8 

28.0 

28.1 

28.2 

28-3 

28.4 

28.6 

28.7 

28.9 

28.4 

28.5 

28.6 

28.7 

28.8 

29.0 

29.1 

29.2 

29.4 

29-5 

29.7 

29.8 

29.9 

29.4 

29-5 

29.6 

29.8 

29.9 

30.1 

30.2 

30-3 

30-4 

30-5 

30-7 

3°-9 

31.0 

30-4 

30-5 

30-7 

30.8 

30.9 

3I-I 

31.2 

31-3 

31-5 

31-6 

31.8 

31-9 

32.1 

31-4 

3i-5 

3i-7 

31-8 

32.0 

32.2 

32.2 

32.4 

32.5 

32.6 

32.8 

33-o 

33-i 

32.5 

32-6 

32.7 

32.9 

33-o 

33-2 

33-3 

33-4 

33-6 

33-7 

339 

34-o 

34-2 

33-5 

33-6 

33-8 

33-9 

34-0 

34-2 

34-3 

34-5 

34-6 

34-7 

34-9 

35-i 

35-2 

34-5 

34-6 

34-8 

.34-9 

35-0 

35-2 

35-3 

35-5 

35-6 

35-8 

36.0 

36.1 

36.3 

35-5 

35-6 

35-8 

35-9 

36.1 

36.2  36.4 

36.5 

36.7 

36.8 

37-o 

37-2 

37-3 

17.2 

17.7 

18.3 

i8.8 

19.4 

20 

20.5 

21.  1 

21.6 

22.2 

22.7 

23-3 

23.8 

18 


2O2  FOOD    ANALYSIS 

dish  from  5  to  8  cm.  in  diameter.  Nickel  crucible-covers  are 
suitable.  When  greater  accuracy  is  required,  and  especially 
when  the  ash  is  to  be  determined,  platinum  dishes  must  be 
used.  Satisfactory  results  may  be  secured  by  the  following 
simple  method  :  A  flat  platinum  dish,  3.5  cm.  in  diameter, 
with  sides  o.  5  cm.  high,  is  provided  with  a  thin  flat  watch- 
glass  cover  that  fits  rather  closely.  The  total  weight  of  the 
cover  and  dish  is  noted.  2  or  3  c.c.  of  the  sample  are  run 
into  the  dish  from  the  pipet,  the  watch-glass  placed  on,  and 
the  weight  taken  as  rapidly  as  possible.  The  glass  prevents 
appreciable  loss  from  evaporation  during  an  ordinary  weighing. 
The  cover  is  removed,  the  dish  heated  on  the  water-bath  or 
in  the  water-oven,  and  weighed  from  time  to  time  (with  cover 
on  it)  until  the  weight  is  sensibly  constant.  The  percentage 
of  residue  can  be  easily  calculated.  About  three  hours  may 
be  required  to  secure  constant  weight. 

The  following  are  the  methods  adopted  by  the  A.  O.  A.  C.  : 

1.  Heat  to  constant  weight  at  the  temperature  of  boiling 
water  from  I  to  2  grams  of  milk  in  a  tared  flat  dish  of  not  less 
than    5  cm.  diameter.      If  desired,   from   15  to   20  grams   of 
pure  dry  sand  may  be  previously  placed  in  the  dish. 

2.  Babcock  Asbestos  Method. — Provide  a  hollow  cylinder  of 
perforated  sheet  metal  60  mm.  long  and  20  mm.  in  diameter, 
closed  5  mm.  from  one  end  by  a  disk  of  the  same  material. 
The  perforations  should  be  about  0.7  mm.  in  diameter  and  0.7 
mm.  apart.      Fill  the  cylinder  loosely  with  from  1.5  to   2.5 
grams  of  freshly  ignited  woolly  asbestos  free  from  fine  or.  brittle 
material.      Cool    in    a    desiccator    and    weigh.      Introduce    a 
weighed  quantity  of  milk  (about  4  grams)  and  dry  at  100°  to 
constant    weight.     The    residue    may  be    employed   for   the 
determination  of  the  fat. 

Ash. — The  residue  from  the  determination  of  total  solids  is 
heated  cautiously  over  the  Bunsen  burner,  until  a  white  ash 
is  left.  The  result  obtained  in  this  manner  is  apt  to  be  slightly 


MILK    AND    MILK    PRODUCTS 

low  from  loss  of  sodium  chlorid.  This  may  be  avoided  by 
heating  the  residue  sufficiently  to  char  it,  extracting  the  sol- 
uble matter  with  a  few  cubic  centimeters  of  water,  and  filtering 
(using  paper  extracted  with  hydrofluoric  acid).  The  filter  is 
added  to  the  residue,  the  whole  ashed,  the  filtrate  then  added, 
and  the  liquid  evaporated  carefully  to  dry  ness.  The  ash  of 
normal  milk  is  about  0.7  per  cent,  and  faintly  alkaline.  A 
marked  degree  of  alkalinity  and  effervescence  with  hydro- 
chloric acid  will  suggest  the  addition  of  a  carbonate. 

The  method  of  the  A.  O.  A.  C.  is  as  follows :  In  a 
weighed  dish  put  20  c.c.  of  milk  from  a  weighing  bottle  ;  add 
6  c.c.  of  nitric  acid,  evaporate  to  dryness,  and  burn  at  a  low 
red  heat  till  the  ash  is  free  from  carbon. 

Fat. — Many  methods  for  fat  determination  have  been 
devised.  The  following  will  suffice  for  all  practical  work  : 

.  Adams'  Method. — This  consists  essentially  in  spreading  the 
milk  over  absorbent  paper,  drying,  and  extracting  the  fat  in  an 
extraction  apparatus  ;  the  milk  is  distributed  in  an  extremely 
thin  layer,  and  by  a  selective  action  of  the  paper  the  larger 
portion  of  the  fat  is  left  on  the  surface.  A  paper,  manufac- 
tured especially  for  this  purpose  by  Schleicher  &  Schuell,  is 
obtainable  in  strips  of  suitable  size.  Each  of  these  yields  to 
ether  only  from  o.ooi  to  0.002  gram  of  extract. 

The  procedure  recommended  by  the  A.  O.  A.  C.  is  as  fol- 
lows :  » 

Coils  made  of  thick  filter-paper,  cut  into  strips  6.25  by 
62.5  cm.,  are  thoroughly  extracted  with  ether  and  alcohol, 
or  the  weight  of  the  extract  corrected  by  a  constant  obtained 
for  the  paper.  From  a  weighing  bottle  about  5  grams  of  the 
milk  are  transferred  to  the  coil  by  means  of  a  pipet,  care 
being  taken  to  keep  dry  the  end  of  the  coil  held  in  the 
fingers.  The  coil  is  placed,  dry  end  down,  on  a  piece  of 
glass  and  dried  at  the  temperature  of  boiling  water  for  one 
hour,  preferably  in  an  atmosphere  of  hydrogen  ;  it  is  then 


2O4  FOOD    ANALYSIS 

transferred  to  an  extraction  apparatus  and  extracted  with  ab- 
solute ether  or  petroleum  spirit  of  boiling-point  about  45°. 
The  extracted  fat  is  dried  in  hydrogen  and  weighed. 

The  above  procedure  is  very  satisfactory,  but  the  drying 
in  hydrogen  may  usually  be  omitted.  After  the  coil  has 
received  at  least  ten  or  twelve  washings,  the  flask  is  detached, 
the  ether  removed  by  distillation,  and  the  fat  dried  by  heating 
in  an  air-oven  at  about  105°,  and  occasionally  blowing  air 
through  the  flask.  After  cooling,  the  flask  is  wiped  with  a 
piece  of  silk,  allowed  to  stand  ten  minutes,  and  weighed. 

H.  D.  Richmond  states  that  to  perform  a  rigidly  accurate 
determination  attention  to  the  following  points  is  necessary  : 
The  ether  must  be  anhydrous  (drying  over  calcium  chlorid 
and  distilling  is  sufficient).  Schleicher  &  Schuell's  fat-free 
papers  should  be  used,  and  one  should  be  extracted  without 
any  milk  on  it,  as  a  tare  for  the  others.  Four  or  five  hours' 
extraction  is  necessary,  and  the  coils  should  be  well  dried 
before  extraction  is  begun. 

Thimble-shaped  cases  made  of  fat-free  paper  are  nowr 
obtainable  and  are  convenient  for  holding  the  absorbent 
material  on  which  the  milk  is  spread.  The  fine  texture  pre- 
vents undissolved  matter  escaping.  A  case  may  be  used 
repeatedly.  Sour  milk  must  be  thinned  with  ammonium 
hydroxid  before  taking  the  portion  for  analysis. 

BabcocK s  extraction  method  is  also  recommended  by  the 
A.  O.  A.  C.  The  cylinder  containing  the  residue  from  the 
determination  of  total  solids  (page  202)  is  placed  in  the 
extraction  tube  and  extracted  with  ether  in  the  usual  way. 
The  ether  is  evaporated  and  the  fat  weighed,  or  the  extracted 
cylinder  may  be  dried  at  100°  and  the  fat  determined  by  the 
loss  in  weight.  As  before,  a  higher  degree  of  accuracy  is 
secured  by  performing  the  drying  operation  in  hydrogen. 

Werner-Schmid  Method. — This  is  suitable  for  sour  milk. 

10  c.c.  of  the  milk  are  measured  into  a  long  test-tube  of  50 


MILK  AND  MILK  PRODUCTS 


205 


c.c.  capacity,  and  10  c.c.  of  strong  hydrochloric  acid  added, 
or  the  milk  may  be  weighed  in  a  small  beaker  and  washed 
into  the  tube  with  the  acid.  After  mixing,  the  liquid  is  boiled 
I  y2  minutes,  or  the  tube  may  be  corked  and  heated  in  the 
water-bath  from  5  to  10  minutes,  until  the  liquid  turns  dark 
brown.  It  must  not  be  allowed  to  turn  black.  The  tube 
and  contents  are  cooled  in  water,  30  c.c.  of  well-washed  ether 
added,  shaken,  and  allowed  to  stand  until  the  line  of  acid  and 
ether  is  distinct.  The  cork  is  taken  out, 
and  a  double-tube  arrangement,  like  that 
of  the  ordinary  wash-bottle,  inserted.  The 
stopper  of  this  should  be  of  cork  and  not 
of  rubber,  since  it  is  difficult  to  slide  the 
glass  tube  in  rubber,  and  there  is  a  possi- 
bility, also,  of  the  ether  acting  on  the 
rubber  and  dissolving  it.  The  lower  end 
of  the  exit-tube  is  adjusted  so  as  to  rest 
immediately  above  the  junction  of  the 
two  liquids.  The  ethereal  solution  of  the 
fat  is  then  blown  out  and  received  in  a 
weighed  flask.  Two  more  portions  of 
ether,  10  c.c.  each,  are  shaken  with  the 
acid  liquid,  blown  out,  and  added  to  the 
first.  The  ether  is  then  distilled  off  and  FIG.  45. 

the  fat  dried  and  weighed  as  above. 

Centrifugal  Methods. — Among  the  processes  for  the  rapid 
determination  of  fat,  those  employing  centrifugal  action  have 
been  found  most  convenient.  The  following  method,  devised 
by  H.  Leffmann  and  W.  Beam  in  1889,  has  proved  satisfac- 
tory on  the  score  of  accuracy,  simplicity,  and  ease  of  manipu- 
lation. The  distinctive  feature  is  the  use  of  fusel  oil,  the 
effect  of  which  is  to  produce  a  greater  difference  in  surface 
tension  between  the  fat  and  the  liquid  in  which  it  is  sus- 
pended, and  thus  promote  its  readier  separation.  This  effect 


206  FOOD    ANALYSIS 

has  been  found  to  be  heightened  by  the  presence  of  a  small 
amount  of  hydrochloric  acid. 

The  test-bottles  have  a  capacity  of  about  30  c.c.  and  are 
provided  with  a  graduated  neck,  each  division  of  which  repre- 
sents o.  I  per  cent,  by  weight  of  butter  fat. 

15  c.c.  of  the  milk  are  measured  into  the  bottle,  3  c.c.  of  a 
mixture  of  equal  parts  of  amyl  alcohol  and  strong  hydro- 
chloric acid  added,  mixed,  the  bottle  filled  nearly  to  the  neck 
with  concentrated  sulfuric  acid,  and  the  liquids  mixed  by 
holding  the  bottle  by  the  neck  and  giving  it  a  gyratory  mo- 
tion. The  neck  is  now  filled  to  about  the  zero  point  with  a 
mixture  of  sulfuric  acid  and  water  prepared  at  the  time.  It 
is  then  placed  in  the  centrifugal  machine,  which  is  so  arranged 
that  when  at  rest  the  bottles  are  in  a  vertical  position.  If 
only  one  test  is  to  be  made,  the  equilibrium  of  the  machine  is 
maintained  by  means  of  a  test-bottle,  or  bottles,  filled  with  a 
mixture  of  equal  parts  of  sulfuric  acid  and  water.  After  rota- 
tion for  from  one  to  two  minutes,  the  fat  will  collect  in  the 
neck  of  the  bottle  and  the  percentage  may  be  read  off.  It  is 
convenient  to  use  a  pair  of  dividers  in  making  the  reading. 
The  legs  of  these  are  placed  at  the  upper  and  lower  limits 
respectively  of  the  fat,  allowance  being  made  for  the  menis- 
cus ;  one  leg  is  then  placed  at  the  zero  point  and  the  reading 
made  with  the  other.  Experience  by  analysts  in  various 
parts  of  the  world  has  shown  that  with  properly  graduated 
bottles  the  results  are  reliable.  As  a  rule,  they  do  not  differ 
more  than  o.  I  of  I  per  cent,  from  those  obtained  by  the 
Adams  process,  and  are  generally  even  closer. 

For  accurate  work,  the  factor  for  correcting  the  reading  on 
each  of  the  bottles  should  be  determined  by  comparison  with 
the  figures  obtained  by  the  Adams  or  other  standard  process. 

Cream  is  to  be  diluted  to  exactly  ten  times  its  volume, 
the  specific  gravity  taken,  and  the  liquid  treated  as  a  milk. 
Since  in  the  graduation  of  the  test-bottles  a  specific  gravity 


MILK  AND  MILK  PRODUCTS  2O? 

of  1.030  is  assumed,  the  reading  must  be  increased  in  pro- 
portion. 

A  more  accurate  result  may  be  obtained. by  weighing  in  the 
test-bottle  about  2  c.c.  of  the  cream  and  diluting  to  about 
15  c.c.  The  reading  obtained  is  to  be  multiplied  by  15.45 
and  divided  by  the  weight  in  grams  of  cream  taken. 

The  mixture  of  fusel  oil  and  hydrochloric  acid  seems  to  be- 
come less  satisfactory  when  long  kept.  It  is  best,  therefore, 
not  to  make  up  large  amounts  at  once.  The  mixture  should 
be  clear  and  not  very  dark  in  color.  It  is  best  kept  in  a  bottle 
provided  with  a  pipet  which  can  be  filled  to  the  mark  by 
dipping.  Rigid  accuracy  in  the  measurement  is  not  needed. 

Calculation  Methods. — Several  investigators  have  proposed 
formulae  by  which  when  any  two  of  the  data,  specific  gravity, 
fat,  and  total  solids,  are  known,  the  third  can  be  calculated. 
These  vary  according  to  the  method  of  analysis  employed. 
That  of  O.  Hehner  and  H.  D.  Richmond,  as  corrected  by 
Richmond,  was  deduced  from  results  by  the  Adams  method 
of  fat  extraction,  and  has  been  found  to  be  the  most  satisfactory. 
It  is  as  follows  : 

T  =  0.25  G  -j-  1.2  F  -f  0.14; 

in  which  T  is  the  total  solids,  G  the  last  two  figures  of  the 
specific  gravity  (water  being  1000),  and  F  the  fat.  A  table 
based  upon  this  formula  is  annexed  (p.  208). 

A  formula  has  been  devised  by  Richmond  by  which  the 
lactose  and  proteids  may  be  calculated  (approximately),  the 
specific  gravity,  fat,  total  solids,  and  ash  being  known.  Thus  : 

P  =  2.8  T  +  2.5  A  —  3.33  F  —  0.7  -£- 

in  which  Pis  the  proteids,  Tthe  total  solids,  A  the  ash,  .Fthe 
fat,  D  specific  gravity  (water  at  15.5°  being  taken  as  i),  and 
G  i  ooo  D —  i  ooo. 2  3 


208 


FOOD    ANALYSIS 


r^      O       PJ       to      r^      O 

t^Q\O        M        CS        Tf 


cxo 

4 


00 

CO 


M        PJ        P) 


M         P<        PI        PI        PI        PI 


PJ        PJ        PJ 


to      vO       00        ON       O 

PJ'      PJ'      PJ'      pi      <o 


O        mvn 


cxj        O 

M        ro 


rovooo 


covO 
O\O 
M  PJ 


M        rovOOO        >-< 
rOrJ-vovOOO 

Pj'        pj        PJ"        PJ'        P) 


fOvOOO        M        ro 
Q\O        w        ro^ 

pj        ro       fO       ro       ro 


rt-vo        O\H4 
O\O        »-i        rO 


ON 

vO 


ONO         HH         CO 


rj- 
rf 


CN 
vO 


tooo        O 


ON       O         PJ 

M"       pj       PJ' 


to        t^        O         <O       to 
Pj'         PJ         Pj'         Pj'         Pj' 


COVOOO        M 


»H        roiOOO        w 


vO        ONM 


ONPJ 

O       PJ 


ONNH 

O       PJ 


ONO        PJ 


M  M  PJ  PJ 


ON        PJ 
O          O 


Tf       t^       ON 
!->.      00         ON 

d      6      o' 


MQMMMMMMPJ 


MILK    AND    MILK    PRODUCTS 

The  difference  between  the  total  solids  and  the  fat,  proteids, 
and  ash  gives  the  lactose.  In  this  formula  it  has  been  assumed 
that  everything  that  is  not  fat,  proteids,  nor  ash  is  milk-sugar  ; 
an  assumption  which  is  not  strictly  correct,  and  which  intro- 
duces a  small  error.  Another  error  is  introduced  by  the  fact 
that  the  ash  in  milk  is  not  the  same  as  the  salts  existing  in  the 
milk.  The  errors  between  the  proteids  and  lactose  found  and 
calculated  vary  between  ±  0.4. 

Total  Proteids. — For  practical  purposes  the  total  pro- 
teids are  best  estimated  by  calculation  from  the  total  nitrogen 
obtained  by  the  Kjeldahl-Gunning  method.  Milk  contains, 
however,  a  sensible  proportion  of  non-proteid  nitrogen.  Ac- 
cording to  Munk,  this  may  range,  in  cows'  milk,  from  0.022 
to  0.034  per  cent.,  and  from  0.014  to  0.026  per  cent,  in 
human  milk.  According  to  these  figures,  the  average  pro- 
teid  nitrogen  in  cows'  milk  would  be  94  per  cent.,  and  in 
human  milk  91  per  cent.,  of  the  total  nitrogen. 

The  determination  of  total  nitrogen  as  recommended  by 
the  A.  O.  A.  C.  is  to  place  in  the  digestion  flask  a  known 
weight  (about  5  grams)  of  the  sample  and  proceed,  without 
evaporation,  as  described  on  page  44.  The  factor  used  to 
convert  nitrogen  to  proteids  is  6.25. 

Ritthausen  Method. — This  method  depends  on  precipitation 
by  copper  sulfate  and  sodium  hydroxid.  It  is  applicable 
only  to  fully  developed  milks  ;  the  proteids  of  colostrum  and 
whey  are  only  partially  precipitated.  The  reagents  are  given 
on  page  1 16. 

10  grams  of  milk  are  placed  in  a  beaker,  diluted  with 
100  c.c.  of  distilled  water,  5  c.c.  of  copper  sulfate  solution 
added,  and  thoroughly  mixed.  The  sodium  hydroxid  solu- 
tion is  then  added  drop  by  drop,  with  constant  stirring, 
until  the  precipitate  settles  quickly  and  the  liquid  is  neutral, 
or  at  most  very  feebly  acid.  An  excess  of  alkali  will  prevent 
the  precipitation  of  some  of  the  proteids. 


210  FOOD    ANALYSIS 

The  reaction  should  be  tested  on  a  drop  of  the  clear  liquid, 
withdrawing  it  by  means  of  a  rod,  taking  care  not  to  include 
any  solid  particles.  When  the  operation  is  correctly  per- 
formed, the  precipitate,  which  includes  the  fat,  settles  quickly, 
and  carries  down  all  of  the  copper.  It  is  washed  by  decanta- 
tion  with  about  100  c.c.  of  water,  and  collected  on  a  filter 
(previously  dried  at  130°  and  weighed  in  a  weighing  bottle). 
The  portions  adhering  to  the  sides  of  the  beaker  are  dis- 
lodged with  the  aid  of  a  rubber-tipped  rod.  The  contents  of 
the  filter  are  washed  with  water  until  250  c.c.  are  collected, 
which  are  mixed  and  reserved  for  the  determination  of  the 
sugar  as  described  below.  The  water  in  the  precipitate  is 
removed  by  washing  once  with  strong  alcohol,  and  the  fat  by 
six  or  eight  washings  with  ether.  An  extraction  apparatus 
may  be  used  for  this  purpose.  The  washings  being  received 
in  a  weighed  flask,  the  determination  of  the  fat  may  be  made 
by  evaporating  the  ether,  with  the  usual  precautions. 

The  residue  on  the  filter,  which  consists  of  the  proteids  in 
association  with  copper  hydroxid,  is  washed  with  absolute 
alcohol,  which  renders  it  more  granular,  and  then  dried  at 
130°  in  the  air-bath.  It  is  weighed  in  a  weighing  bottle, 
transferred  to  a  porcelain  crucible,  incinerated,  and  the  resi- 
due again  weighed.  The  weight  of  the  filter  and  contents, 
less  that  of  the  filter  and  residue  after  ignition,  gives  the 
weight  of  the  proteids.  The  results  by  this  method  are 
slightly  high,  since  copper  hydroxid  does  not  become  com- 
pletely converted  into  copper  oxid  at  130.° 

Casein  and  Albumin. — The  most  accurate  separation  of 
casein  and  albumin  is  made  by  Sebelein's  method,  as  follows  : 
20  c.c.  of  the  sample  are  mixed  with  40  c.c.  of  a  saturated 
solution  of  magnesium  sulfate  and  powered  magnesium  sul- 
fate  stirred  in  until  no  more  will  dissolve.  The  precipitate 
of  casein  and  fat,  including  the  trace  of  globulin,  is  allowed  to 
settle,  filtered,  and  washed  several  times  with  a  saturated 


MILK    AND    MILK    PRODUCTS  211 

solution  of  magnesium  sulfate.  The  filtrate  and  washings 
are  saved  for  the  determination  of  albumin.  The  filter  and 
contents  are  transferred  to  a  flask  and  the  nitrogen  deter- 
mined by  the  method  described  above.  The  nitrogen  so 
found,  multiplied  by  6.38,  gives  the  casein. 

The  filtrate  and  washings  from  the  determination  of  casein 
are  mixed,  the  albumin  precipitated  by  Almen's  tannin  reagent, 
filtered,  and  the  nitrogen  in  the  precipitate  determined  as 
above.  The  same  factor  is  used. 

A/men's  reagent  is  prepared  by  dissolving  4  grams  of  tan- 
nin in  190  c.c.  of  50  per  cent,  alcohol  and  adding  8  c.c.  of 
acetic  acid  of  25  per  cent. 

H.  D.  Richmond  and  L.  K.  Boseley  have  modified  the  Ritt- 
hausen  process  by  diluting  the  milk  to  200  c.c.,  adding  a  little 
phenolphthalein,  and  neutralizing  any  acidity  by  the  cautious 
addition  of  dilute  sodium  hydroxid  solution,  then  adding  from 
2.0  to  2.5  c.c.  of  the  copper  sulfate  solution.  The  precipitate 
is  allowed  to  settle,  washed,  and  estimated  as  above. 

This  modification  was  found  to  give  good  results  with  all 
milk  products  except  whey,  which  contains  albumoses  pro- 
duced by  the  action  of  rennet.  In  a  mixture  of  milk  and 
whey  in  about  equal  parts,  Richmond  and  Boseley  found  about 
0.3  per  cent,  of  albumoses  not  precipitated  by  the  copper  sul- 
fate nor  by  magnesium  sulfate,  but  precipitable,  along  with  the 
albumin,  by  a  solution  of  tannin.  The  separation  may  be 
effected  by  diluting  the  filtrate  from  the  magnesium  sulfate 
precipitation,  acidifying  slightly  with  acetic  acid,  and  boiling, 
when  the  albumin  will  be  coagulated  and  precipitated.  The 
albumoses  may  be  separated  by  filtering  the  solution  and  pre- 
cipitating with  tannin  solution.  The  precipitated  proteids  are 
best  estimated  by  determining  the  nitrogen  in  the  moist  pre- 
cipitate. The  separation  of  the  proteids  may  be  effected,  though 
less  accurately,  by  the  use  of  acetic  acid,  as  recommended  by 


212  FOOD    ANALYSIS 

Hoppe-Seyler  and  Ritthausen.     The  following  methods  have 
been  provisionally  adopted  by  the  A.  O.  A.  C.  : 

1.  Provisional  Method  for  the  Determination    of   Casein  in 
Cows'  Milk. — The  determination  should  be  made  when  the 
milk  is  fresh.      When  it  is  not  practicable  to  make  the  deter- 
mination within   24  hours,  add  one  part  of  formaldehyde  to 

.2500  parts  of  milk  and  keep  in  a  cool  place.  10  grams  of  the 
sample  are  diluted  with  about  90  c.c.  of  water  at  between  40° 
and  42°  and  1.5  c.c.  of  a  solution  containing  10  per  cent,  of 
acetic  acid  by  weight,  allowed  to  stand  for  five  minutes, 
washed  three  times  by  decantation,  pouring  the  washings 
through  a  filter,  and  the  precipitate  transferred  completely  to 
the  filter.  If  the  filtrate  is  not  clear  at  first,  it  will  generally 
become  so  in  two  or  three  filtrations,  after  which  the  washing 
can  be  completed.  The  nitrogen  in  the  washed  precipitate 
and  filter  is  determined  by  the  Kjeldahl-Gunning  method. 
The  nitrogen,  multiplied  by  6.25,  gives  the  casein. 

In  working  with  milk  which  has  been  kept  with  preserva- 
tives, the  acetic  acid  should  be  added  in  small  portions,  a  few 
drops  at  a  time  with  stirring,  and  the  addition  continued  until 
the  liquid  above  the  precipitate  becomes  clear  or  nearly  so. 

2.  Provisional  Method  for  the  Determination  of  Albumin  in 
Milk. — The  filtrate  obtained  in  the  above  operation  is  neutral- 
ized with  sodium  hydroxid,  0.3   c.c.  of  the  10  per  cent,  solu- 
tion  of  acetic  acid    added,   and    the    mixture  heated   for    1 5 
minutes.     The  precipitate  is  collected  on  a  filter,  washed,  and 
the  nitrogen  determined. 

We  have  found  the  following  method  satisfactory,  avoiding 
the  difficulty  of  washing  the  precipitate  :  10  c.c.  of  the  milk 
are  mixed  with  saturated  magnesium  sulfate  solution  and  the 
powdered  salt  added  to  saturation.  The  mixture  is  washed 
into  a  graduated  measure  with  a  small  amount  of  the  saturated 
solution,  made  up  to  100  c.c.  with  the  same  solution,  mixed, 
and  allowed  to  stand  until  the  separation  takes  place.  As 


MILK  AND  MILK  PRODUCTS  213 

much  as  possible  of  the  clear  portion  is  drawn  off  with  a  pipet 
and  passed  through  a  dry  filter.  An  aliquot  portion  of  the 
filtrate  is  taken,  the  albumin  precipitated  by  a  solution  of 
tannin,  and  the  nitrogen  in  the  precipitate  determined  as 
above. 

The  casein  is  found  by  subtracting  the  figure  for  albumin 
from  that  for  total  proteids. 

Lactose. — Soxhlet's  method,  adopted  by  the  A.  O.  A.  C., 
is  as  follows  :  25  c.c.  of  the  sample  in  a  500  c.c.  flask  are 
diluted  with  400  c.c.  of  water  and  10  c.c.  of  copper  sulfate 
solution  (34.639  grams  crystallized  copper  sulfate  in  500  c.c.) 
and  8.8  c.c.  ^  sodium  hydroxid  solution  added.  (The  mix- 
ture should  still  have  an  acid  reaction  and  contain  copper  in 
solution.  If  this  is  not  the  case,  the  experiment  must  be 
repeated,  using  a  little  less  of  the  alkali.)  The  flask  is  filled 
to  the  mark  with  water,  shaken,  and  the  liquid  passed  through 
a  dry  filter.  50  c.c.  of  the  mixed  copper  reagent  (page  116) 
are  heated  to  brisk  boiling  in  a  300  c.c.  beaker,  100  c.c.  of 
the  filtrate  obtained  as  above  added,  and  boiling  continued  for 
six  minutes  ;  the  liquid  then  promptly  filtered,  and  treated  ac- 
cording to  methods  given  on  pages  120  to  122.  The  amount 
of  lactose  is  calculated  from  the  copper  obtained  by  the  table 
on  page  214.  The  figures  for  weights  of  copper  between  any 
two  data  given  in  the  table  may  be  calculated  with  sufficient 
accuracy  for  practical  purposes  by  allowing  0.0608  gram  of 
lactose  for  each  o.ooi  gram  of  copper. 

Lactose  may  be  determined  by  the  polarimeter  after  re- 
moval of  the  fat  and  proteids,  which  is  best  effected,  as  recom- 
mended by  H.  W.  Wiley,  by  a  mercuric  nitrate  solution,  pre- 
pared by  dissolving  mercury  in  twice  its  weight  of  nitric  acid 
of  1.42  sp  gr.  and  adding  to  the  solution  five  volumes  of 
water. 

60  c.c.  of  the  milk  are  placed  in  a  100  c.c.  flask  and  10  c.c. 
of  the  mercuric  solution  added.  The  flask  is  filled  to  the 


214 


FOOD    ANALYSIS 


mark  with  water,  well  shaken,  and  the  liquid  filtered  through 
a  dry  filter.  The  filtrate,  which  will  be  perfectly  clear,  may 
be  examined  at  once  in  the  polarimeter.  Several  readings 
should  be  made  and  the  average  taken. 


COPPER. 

LACTOSE. 

COPPER. 

LACTOSE. 

COPPER. 

LACTOSE. 

0.  100 

0.072 

0.205 

0.151 

0.305 

0.228 

0.105 

0.075 

0.210 

0.154 

0.310 

0.232 

O.I  10 

0.079 

0.215 

0.158 

0.315 

0.236 

0.115 

0.083 

O.22O 

0.162 

0.320 

0.240 

0.120 

0086 

0.225 

0.165 

0.325 

0.244 

O.I25 

0.090 

0.230 

0.169 

0-33° 

0.248 

0.130 

0.094 

0.235 

0.173 

0-335 

0.252 

0.135 

0.097 

0.240 

0.177 

0.340 

0.256 

0.140 

O.IOI 

0.245 

0.181 

0-345 

0.260 

0.145 

0.105 

0.250 

0.185 

0.350 

0.264 

0.150 

0.109 

0.255 

0.189 

0-355 

0.268 

0-155 

0.  112 

0.260 

0.192 

0.360 

0.272 

o.  1  60 

0.116 

0.265 

0.196 

0.365 

0.276 

0.165 

0.120 

0.270 

O.2OO 

0.370 

0.280 

0.170 

o.  124 

0.275 

0.204 

0-375 

0.285 

0.175 

0.128 

0.280 

O.2O8 

0.380 

0.289 

0.180 

0.132 

0.285 

0.212 

0.385 

0.293 

0.185 

0.134 

0.290 

0.216 

0.390 

0.298 

0.190 

0.139 

0.295 

O.22I 

0-395 

0.302 

0.195 

0.141 

0.300 

8.224 

0.400 

0.306 

O.2OO 

0.147 

It  is  to  be  noted  that  the  actual  volume  of  the  sugar-con- 
taining solution  is  100  c.c.,  less  the  space  occupied  by  the 
precipitated  proteids  and  fat.  The  volume  of  fat  is  found  by 
multiplying  the  weight  in  grams  by  1.075  and  the  proteids  by 
multiplying  the  weight  by  0.8. 

P.  Vieth  recommends  adding  mercuric  solution  in  the  pro- 
portion of  3  c.c.  to  100  c.c.  of  the  milk,  when  the  whey  will  oc- 
cupy the  same  volume  as  the  original  milk,  less  that  of  the 


MILK  AND  MILK  PRODUCTS  215 

fat,  since,  for  all  practical  purposes,  3  c.c.  may  be   taken  as 
the  volume  of  the  albuminoids  precipitated. 

The  employment  of  a  factor  for  correcting  for  the  volume 
of  precipitate  may  be  avoided  by  Scheibler's  method  of"  double 
dilution"  (see  page  30),  in  which  two  solutions  of  different 
volume  are  compared.  The  following  is  a  summary  of  the 
method  given  by  H.  W.  Wiley  and  E.  E.  Ewell  24:  The  polari- 
meter  used  in  this  experiment  was  adapted  to  a  normal  weight 
of  26.048  sucrose,  and  32.91  grams  of  lactose  in  100  c.c.  gave 
a  reading  of  100.  The  amount  of  milk  taken  was  double  this 
quantity,  65.82  grams,  which  were  placed  in  a  100  c.c.  flask,  10 
c.c.  of  the  acid  mercuric  nitrate  added,  the  flask  filled  to  the  mark 
the  contents  well  mixed,  filtered,  and  polarized.  A  similar  quan- 
tity of  the  milk  was  placed  in  a  200  c.c.  flask  and  treated  in 
the  same  way.  The  true  polarization  is  obtained  by  dividing 
the  product  of  the  readings  in  the  two  flasks  by  their  difference. 
The  following  experiments  are  given  by  Wiley  and  Ewell : 

READING  IN  200       READING  IN  100      APPARENT  PERCENT-       TRUE  PERCENT- 
c.c.  FI.ASK.  c.c.  FLASK.  AGE  LACTOSE.  AGE  LACTOSE. 

10.15  20.84  5-2i  4.95 

The  polarimeter  used  had  a  tube  4  decimeters  long.  The 
figure  for  apparent  percentage  is  obtained  by  dividing  the 
reading  of  the  small  flask  by  4.  The  true  percentage  is 
obtained  by  multiplying  10.15  by  20.84,  dividing  by  their 
difference  (10.69),  and  taking  one-fourth  this  quotient. 

Unless  the  instrument  be  highly  accurate,  and  great  care  be 
taken  in  the  work,  the  results  are  less  satisfactory  than  by  the 
method  first  described,  in  which  an  allowance  is  made  for  the 
volume  of  the  precipitate. 

Birotation. — When  freshly  dissolved  in  cold  water,  milk 
sugar  shows  a  higher  rotation  than  that  given  above.  By 
standing,  or  immediately  on  boiling,  the  rotatory  power  falls 
to  the  point  mentioned.  In  preparing  solutions  from  the  solid 
milk-sugar,  care  must  be  taken  to  bring  them  to  the  boiling- 


2l6  FOOD    ANALYSIS 

point  previous  to  making  up  a  definite  volume.  This  pre- 
caution is  unnecessary  when  operating  upon  milk. 

Adulterations. — The  addition  of  water  to  milk  is  usually 
detected  by  the  diminution  in  the  amount  of  solids. 

The  addition  of  water  decreases  the  specific  gravity,  while 
abstraction  of  fat  increases  it. 

P.  Vieth  has  pointed  out  that  in  normal  milks  the  ratio 
sugar  :  proteids  :  ash  =  13  :  9  :  2  exists,  and  a  determination 
of  these  ratios  may  aid  in  the  attempt  to  distinguish  genuine 
but  abnormal  milks  from  watered  milks.  In  the  case  of  a 
watered  milk  the  proportion  would  remain  unchanged,  but  in 
abnormal  milk  it  has  been  found  to  vary.  H.  D.  Richmond 
finds  that  "the  most  constant  figure  in  normal  milks  is  the 
proportion  of  ash  to  solids  not  fat,  which  averages  8.3  per 
cent,  and  very  rarely  passes  outside  of  the  limits  of  8.0  per 
cent,  and  8.5  per  cent.  In  cases  of  low  solids  not  fat  this 
proportion  has  been  disturbed,  and  the  ash  has  had  a  higher 
ratio  to  the  solids  not  fat."  Other  observers  have  found  the 
same. 

Richmond  also  states  that  when  unadulterated  milk  is 
notably  deficient  in  solids  not  fat,  the  deficiency  is  principally 
in  the  lactose. 

According  to  Richmond,  the  determination  of  the  amount 
of  water  that  has  been  added  to  milk  is  best  calculated 
from  the  figures  obtained  by  adding  the  difference  be- 
tween the  specific  gravity  of  the  sample  and  1000  to  the 
figure  representing  the  percentage  of  the  fat.  Thus,  jf  a  milk 
have  the  specific  gravity  of  1029.2  and  contain  3.27  per  cent, 
of  fat,  the  figure  from  which  the  water  is  calculated  is  29.2  -f- 
3.27  =  32.47.  The  mean  figure  from  unadulterated  milks 
was  found  to  be  36.0,  but  34.5  is  considered  to  be  a  safer 
limit.  Accepting  this  figure,  the  percentage  of  added  water 
in  the  sample  given  above  would  be  found  by  the  proportion : 

34.5  :  32.47   :  :    100  :  94.1  ; 


MILK  AND  MILK  PRODUCTS  217 

i.  e.,  the  sample  would  contain  5.9  per  cent,  of  water.  Ex- 
periments on  milks  which  had  been  diluted  with  known 
proportions  of  water  showed  that  this  method  of  calculating 
the  added  water  gave  nearer  approximations  to  the  truth  than 
by  calculating  from  the  figure  for  non-fatty  solids. 

For  ordinary  milk  control  it  will  suffice  to  take  the  specific 
gravity  by  the  lactodensimeter  (see  page  200)  and  the  fat  by 
the  Leffmann-Beam  method.  From  the  figures  thus  obtained 
the  total  solids  can  be  ascertained  by  the  table  or  Richmond's 
slide-rule. 

Coloring  and  Thickening  Agents. — Several  instances  of  the 
use  of  brain-matter,  dextrin,  and  gelatin  have  been  recorded. 
It  is  also  stated  that  sugar,  salt,  and  starch  have  been  added. 
Coloring-matters  are  used  to  conceal  inferiority  in  quality. 
At  the  present  time  preparations  of  annatto,  turmeric,  and 
some  coal-tar  colors  are  mostly  used,  especially  the  latter. 
Caramel  is  occasionally  used,  saffron  and  carotin  but  rarely. 
Annatto  may  be  detected  by  rendering  the  sample  slightly 
alkaline  by  acid  sodium  carbonate,  immersing  a  slip  of  filter- 
paper,  and  allowing  it  to  remain  overnight.  Annatto  will 
cause  a  reddish-yellow  stain  on  the  paper. 

A.  Leys  gives  the  following  method  for  detecting  annatto  : 
50  c.c.  of  the  sample  are  shaken  with  40  c.c.  of  95  per  cent, 
alcohol,  50  c.c.  of  ether,  3  c.c.  of  water,  and  1.5  c.c.  of 
ammonium  hydroxid  solution  (sp.  gr.  0.900),  and  allowed  to 
stand  for  20  minutes.  The  lower  layer,  which  in  presence  of 
annatto  will  have  a  greenish-yellow  tint,  is  tapped  off  and 
gradually  treated  with  half  its  measure  of  10  per  cent,  solu- 
tion of  sodium  sulfate,  the  separator  being  inverted,  without 
shaking,  after  each  addition.  By  this  treatment  the  casein 
separates  in  flakes,  which  conglomerate  and  rise  to  the  sur- 
face, when  the  adjacent  liquid  is  tapped  off,  strained  through 
wire  gauze,  and  placed  in  four  test-tubes.  To  each  of  these 
amyl  alcohol  is  added,  and  the  tubes  shaken  and  immersed 
19 


218 


FOOD    ANALYSIS 


in  cold  water,  which  is  gradually  raised  to  80°.  This  causes 
the  emulsion  to  break  up,  and  the  alcohol,  holding  the 
annatto  in  solution,  to  come  to  the  surface.  The  alcoholic 
layer  is  separated  from  the  lower  stratum,  evaporated  to  dry- 
ness,  and  the  residue  dissolved  in  warm  water  containing 
a  little  common  alcohol  and  ammonia.  A  bundle  of  white 
cotton  fibers  is  introduced  and  the  liquid  evaporated  nearly  to 
dryness  on  the  water-bath.  The  fiber,  which  is  colored  a 
pale  yellow,  even  with  pure  milk,  is  washed  and  immersed  in 
a  solution  of  citric  acid,  when  it  will  be  immediately  colored 
rose-red  if  the  milk  contained  annatto.  Saffron,  turmeric, 
and  the  coloring-matter  of  marigolds  do  not  give  a  similar 
reaction. 

General  Method  for  Colors  in  Milk. — A.  E.  Leach  2  5  has 
devised  a  general  method  for  detecting  colors  in  milk,  i  50 
c.c.  of  the  sample  are  coagulated  in  a  porcelain  basin,  with 
the  addition  of  acetic  acid  and  heating,  and  the  curd  separated 
from  the  whey.  The  curd  will  often  collect  in  a  mass  ;  but 
if  this  does  not  occur,  it  must  be  freed  from  whey  by  strain- 
ing through  muslin.  The  curd  is  macerated  for  several  hours 
in  a  closed  flask,  with  occasional  shaking,  with  ether  to 
extract  fat.  Annatto  will  also  be  removed  by  it.  The  ether 
and  curd  are  separated  and  treated  as  follows  : 


The  ether  is  evaporated,  the  residue 
mixed  with  some  weak  solution  of 
sodium  hydro x id,  and  passed  through 
a  wet  filter ;  and  when  this  has 
drained,  the  fat  is  washed  off  and  the 
paper  dried.  An  orange  tint  shows 
annatto,  which  may  be  confirmed  by 
a  drop  of  solution  of  stannous  chlorid, 
which  makes  a  pink  spot. 


If  the  curd  be  colorless,  no  foreign  color- 
ing-matter is  in  it ;  if  orange  or  brown, 
it  should  be  shaken  with  strong  hydro- 
chloric acid  in  a  test-tube. 


If  the  mass  turns 
blue  giadually, 
caramel  is  proba- 
bly present.  The 
whey  should  be 
examined  for 
caramel  ( see 
page  130). 


If  the  mass  turns 
pink  at  once,  an 
azo-color  is  indi- 
cated. 


MILK  AND  MILK  PRODUCTS  2IQ 

Coal-tar  colors  may  often  be  detected  by  the  wool-test  (p. 
77),  but  H.  C.  Lythgoe  has  devised  the  following  method, 
which  he  finds  very  satisfactory  :  I  5  c.c.  of  the  sample  are 
Vnixed  in  a  porcelain  basin  with  an  equal  volume  of  hydro- 
chloric acid  (sp.  gr.  1. 20),  and  the  mass  shaken  gently  so -as 
to  break  the  curd  into  coarse  lumps.  If  the  milk  contains  an 
azo-color,  the  curd  will  be  pink  ;  with  normal  milk  the  curd 
will  be  white  or  yellowish.  (See  also  under  "  Butter.") 

Starch  may  be  detected  by  the  blue  color  developed  on  the 
addition  of  solution  of  iodin  to  the  milk. 

Salt  and  cane-sugar  are  occasionally  added  to  milk  that 
has  been  diluted  with  water.  The  former  is  detected  by  the 
taste,  the  increased  proportion  of  ash  and  of  chlorin.  Cane- 
sugar  may  be  detected,  if  in  considerable  quantity,  by  the 
taste.  Cotton  devised  the  following  test:  10  c.c.  of  the 
sample  are  mixed  with  0.5  gram  of  powdered  ammonium 
molybdate,  and  10  c.c.  of  dilute  hydrochloric  acid  (i  to  10) 
are  added.  In  a  second  tube  10  c.c.  of  milk  of  known  purity 
or  10  c.c.  of  a  6  per  cent,  solution  of  milk-sugar  are  similarly 
treated.  The  tubes  are  then  placed  in  the  water-bath  and  the 
temperature  gradually  raised  to  about  80°.  If  sucrose  be 
present,  the  milk  will  assume  an  intense  blue  color,  while 
genuine  milk  or  milk-sugar  remains  unaltered  unless  the 
temperature  be  raised  to  the  boiling-point.  According  to 
Cotton,  the  reaction  is  well  marked  in  the  presence  of  as  little 
as  I  gram  of  sucrose  to  a  liter  of  the  milk,  and  6  grams 
and  over  per  liter  are  usually  found  in  adulterated  samples. 
(See  also  page  1 14.) 

The  quantitative  determination  is  made  by  the  methods 
described  in  connection  with  condensed  milk. 

GELATIN. — A.  W.  Stokes  detects  the  presence  of  gelatin  in 
cream  or  milk  as  follows  :  10  c.c.  of  the  sample,  20  c.c.  of 
cold  water,  and  10  c.c.  of  acid  mercuric  nitrate  solution 
(page  213)  are  mixed,  shaken  vigorously,  allowed  to  stand  for 


22O  FOOD    ANALYSIS 

five  minutes,  and  filtered.  If  much  gelatin  be  present,  it 
will  be  impossible  to  get  a  clear  filtrate.  A  portion  of  the 
filtrate  is  mixed  with  an  equal  bulk  of  saturated  aqueous  solu- 
tion of  picric  acid.  If  any  gelatin  be  present,  a  yellow  pre- 
cipitate will  be  immediately  produced.  Picric  acid  will  detect 
the  presence  of  one  part  of  gelatin  in  10,000  parts  of  water. 

Antiseptic  substances  are  largely  used,  especially  in  the 
warmer  season,  as  a  substitute  for  refrigeration.  Many  of 
these  are  sold  under  proprietary  names  which  give  no  indica- 
tion of  their  composition.  Preparations  of  boric  acid  and 
borax  were  at  one  time  the  most  frequent  in  use,  but  lately 
formalin,  a  40  per  cent,  solution  of  formaldehyde  (methyl 
aldehyde),  has  come  into  favor.  Sodium  benzoate  is  now  in 
common  use  as  a  preservative  of  cider,  fruit-jellies,  and  simi- 
lar articles,  and  may,  therefore,  be  found  in  milk.  Salicylic 
acid  is  not  so  much  employed  as  in  former  years.  Sodium 
carbonate  is  occasionally  used  to  prevent  coagulation  due  to 
slight  souring. 

R.  T.  Thomson  has  studied  the  comparative  value  of  milk 
preservatives.  He  finds  that  a  mixture  of  boric  acid  and 
borax  is  more  efficient  than  the  acid  alone.  The  quantity 
generally  used  is  equivalent  to  about  0.5  gram  of  boric  acid 
per  liter.  Formalin  was  shown  to  be  by  far  the  most  efficient 
antiseptic.  In  the  proportion  of  0.125  gram  to  the  liter,  it 
kept  milk  sweet  for  eight  days. 

Formaldehyde. — The  presence  of  this  body  may  sometimes 
be  detected  by  the  odor  developed  on  warming  the  milk.  O. 
Hehner's  method,  the  most  characteristic  for  its  detection, 
depends  upon  the  fact  that  when  milk  containing  it  is  mixed 
with  sulfuric  acid  containing  a  trace  of  ferric  salt  a  blue  color 
appears.  H.  D.  Richmond  &  L.  K.  Boseley  showed  that  the 
delicacy  of  the  test  is  much  increased  by  diluting  the  milk 
with  an  equal  bulk  of  water  and  adding  sulfuric  acid  of  90  to 
94  per  cent.,  so  that  it  forms  a  layer  underneath  the  milk. 


MILK  AND  MILK  PRODUCTS  221 

Under  these  conditions,  milk,  in  the  absence  of  formaldehyde, 
gives  a  slight  greenish  tinge  at  the  junction  of  the  two  liquids, 
while  a  violet  ring  is  formed  when  formaldehyde  is  present 
even  in  so  small  a  quantity  as  I  part  in  200,000  of  milk.  The 
color  is  permanent  for  two  or  three  days.  In  the  absence  of 
formaldehyde,  a  brownish  color  is  developed  after  some 
hours,  not  at  the  junction  of  the  two  liquids,  but  lower  down 
in  the  acid. 

Hydrochloric  acid  containing  a  small  amount  of  ferric 
chlorid  gives  a  characteristic  violet  with  quantities  of  formal- 
dehyde not  over  i  part  per  1000.  The  test  is  applied  by 
heating  i  c.c.  of  the  sample  with  4  c.c.  of  strong  hydrochloric 
acid.  If  a  yellow  liquid  is  formed,  the  sample  should  be 
diluted  two  or  three  times  and  the  test  repeated.  Hydro- 
chloric acid  often  contains  sufficient  ferric  chlorid  to  give  the 
test.  The  addition  of  0.25  gram  of  ferric  chlorid  to  1000 
c.c.  of  pure  acid  will  be  sufficient. 

The  following  test  has  been  found  satisfactory  by  some 
observers  :  5  c.c.  of  the  sample  are  boiled  with  0.05  gram  of 
resorcinol,  to  which  3  c.c.  of  a  strong  solution  of  sodium 
hydroxid  have  been  added.  If  formaldehyde  be  present,  the 
yellow  solution  changes  to  a  fine  red. 

O.  Hehner  also  gives  the  following  test:  Some  of  the  milk 
is  distilled  and  to  the  distillate  one  drop  of  a  dilute  aqueous 
solution  of  phenol  is  added  and  the  mixture  poured  on  strong 
sulfuric  acid  contained  in  a  test-tube.  A  bright  crimson  zone 
appears  at  the  line  of  contact.  This  color  is  readily  seen  with 
i  part  of  formaldehyde  in  200,000  of  water.  If  there  is  more 
than  i  part  in  100,000,  there  is  seen  above  the  red  ring  a 
white,  milky  zone,  while  in  stronger  solutions  a  copious  white 
or  slightly  pink,  curdy  precipitate  is  obtained. 

The  reaction  succeeds  only  when  carried  out  as  described 
above  ;  the  phenol  must  first  be  mixed  with  the  solution  to  be 
tested,  and  the  mixture  poured  upon  the  sulfuric  acid.  Only 


222  FOOD    ANALYSIS 

a  trace  of  phenol  must  be  used,  and  if  it  be  first  dissolved  in 
the  acid  and  the  formaldehyde  solution  added,  no  color  is 
obtained. 

The  precipitate  might  be  utilized  for  the  determination  of 
the  strength  of  dilute  formalin  solutions. 

The  rate  at  which  formaldehyde  disappears  from  milk  has 
been  investigated  by  Hehner,  who  found  that  at  the  end  of  a 
week  none  could  be  detected  in  a  sample  to  which  had  been 
added  I  part  in  100,000;  after  two  weeks  none  could  be  de- 
tected in  a  sample  of  I  part  in  50,000 ;  and  after  three  weeks 
only  a  faint  trace  could  be  detected  in  a  sample  of  I  part  in 
25,000. 

Determination  of  Formaldehyde. — G.  J.  Romijn  examined 
several  of  the  quantitative  methods  and  found  the  following  to 
be  satisfactory  when  no  other  aldehyde  is  present  in  appre- 
ciable amount : 

10  c.c.  of  the  solution  are  mixed  with  25  c.c.  —  iodin  solu- 

•*  10 

tion  and  sufficient  strong  sodium  hydroxid  solution  added  to 
make  the  liquid  bright  yellow.  After  standing  10  minutes, 
hydrochloric  acid  is  slowly  added  until  a  marked  brown  liquid 
is  produced.  The  iodin  is  then  titrated  with  thiosulfate  in  the 
usual  way.  The  amount  of  iodin  that  has  been  taken  up, 
multiplied  by  o.  1 18,  will  give  the  amount  of  formaldehyde. 

Sodium  Carbonate. — The  following  method,  due  to  E. 
Schmidt,  is  stated  to  be  capable  of  detecting  o.  I  per  cent,  of 
sodium  carbonate  or  of  sodium  acid  carbonate  : 

10  c.c.  of  the  milk  are  mixed  with  an  equal  volume  of 
alcohol,  and  a  few  drops  of  a  I  per  cent,  solution  of  rosolic 
acid  added.  Pure  milk  shows  merely  a  brownish-yellow 
color,  but  in  the  presence  of  sodium  carbonate  a  more  or  less 
marked  rose-red  appears.  The  delicacy  of  the  test  is  en- 
hanced by  making  a  comparison  cylinder  with  the  same 
amount  of  milk  known  to  be  pure.  If  the  salt  is  present  in 


MILK  AND  MILK  PRODUCTS  223 

considerable  amount,  it   may  be  detected  by  the   increase  in 
the  ash,  its  marked  alkalinity  and  effervescence  with  acid. 

Preservation  of  Milk-samples. — Formaldehyde  is  now  gen- 
erally used  ;  0.05  per  cent,  will  keep  milk  for  a  month  and 
larger  quantities  for  an  indefinite  period. 

E.  J.  Bevan  has,  however,  noted  the  fact  that  the  total 
solids  of  milk  containing  formaldehyde  are  always  higher, 
and  that  the  increase  is  much  greater  than  can  be  accounted 
for,  even  assuming  that  the  whole  of  the  formaldehyde  re- 
mains in  the  residue.  Experiments  on  pure  solutions  of 
albumin,  milk-sugar,  and  cane-sugar  showed  in  each  case  an 
increase  in  residue  when  evaporated  with  formaldehyde. 

Detection  of  Boiled  Milk. — R.  Dupouy  proposed  the  fol- 
lowing method  :  A  few  drops  of  a  solution  of  1-4  diamido- 
benzene  in  water  are  added  to  5  c.c.  of  the  sample,  and  then 
a  few  drops  of  hydrogen  dioxid  solution.  Raw  milk  gives  a 
blue  color ;  milk  that  has  been  heated  over  about  79°  gives 
no  color.  The  solution  of  diamidobenzene  must  be  freshly 
prepared.  C.  H.  Rosier  has  found  that  1-3  diamidobenzene 
will  serve,  and  that  if  the  blue  milk  be  shaken  with  amyl 
alcohol,  the  blue  color  passes  into  the  latter  and  is  more 
stable.  These  tests  are  applicable  for  distinguishing  between 
pasteurized  and  sterilized  milks. 

H.  Faber  has  shown  that  raw  milk  may  be  distinguished 
from  boiled  milk  or  milk  that  has  been  heated  above  75°  by 
the  fact  that  such  treatment  coagulates  or  alters  the  albumin 
so  that  if  the  liquid  be  saturated  with  magnesium  sulfate, 
the  albumin  is  separated  along  with  the  albumin  casein. 

H.  D.  Richmond  and  L.  K.  Boseley  recommend  the  fol- 
lowing methods  to  distinguish  new  milk  from  milk  which  has 
been  sterilized  : 

(a)  100  c.c.  of  the  sample  are  allowed  to  stand  in  a  gradu- 
ated cylinder  for  six  hours  at  15.5°  and  the  percentage  of 
cream  noted.  If  less  than  2.5  per  cent,  of  cream  has  risen 


224 


FOOD    ANALYSIS 


for  each  I  per  cent,  of  fat  in  the  milk,  the  milk  may  be  con- 
sidered suspicious  ;  if  the  quantity  of  cream  falls  decidedly 
below  2  per  cent,  for  each  I  per  cent,  of  fat,  it  is  probable 
that  sterilized  milk  is  present. 

(fr)  The  albumin  is  determined  by  means  of  magnesium 
sulfate.  If  less  than  0.35  per  cent,  is  found,  sterilized  milk 
may  be  considered  to  be  present. 

(c)  The  milk-sugar  is  determined  by  the  polarimeter,  and 
also  gravimetrically,  in  duplicate.  If  the  difference  between 
the  two  estimations  be  more  than  0.2  per  cent.,  it  will  be  cor- 
roborative evidence  of  the  presence  of  sterilized  milk.  It  is 
doubtful  whether  a  proportion  of  sterilized  milk  much  below 
30  per  cent,  can  be  detected. 

The  following  figures,  by  C.  H.  Stewart,  show  the  per- 
centage of  soluble  albumin  found  in  milk  raised  to  various 
temperatures  : 

SOLUBLE  ALBUMIN  IN   SOLUBLE  ALBUMIN  IN 


TIME  OF  HEATING. 

FRESH  MILK. 

HEATED  MILK. 

10  minutes  at  60° 

0.423 

0.418 

30                      60° 

0-435 

0.427 

10                      65° 

o-395 

0.362 

30                      65° 

0-395 

0-333 

10                    70° 

0.422 

0.269 

30                    70° 

0.421 

0-253 

10                    75° 

0.380 

0.07 

30                   75° 

0.380 

0.05 

10                    80° 

0-375 

none. 

30                   80° 

0-375 

none. 

INFECTED  MILKS 

Blue  Milk. — Milk  occasionally  becomes  blue  on  the  sur- 
face, the  color  forming  in  patches  in  proportion  as  the  cream 
rises.  The  condition  is  due  to  the  development  of  a  chromo- 
genic  bacillus.  The  condition  sometimes  prevails  in  epidemic 
form.  The  butter  prepared  from  such  milk  possesses  a 
greenish  color  and  a  disagreeable  butyric  odor. 

Red  milk  is  due  to  accidental  contamination  with  the  Ba- 


CONDENSED     MILK  22  5 

cillus  prodigiosus  and  several  other  forms.  The  spores  of 
these  microbes  exist  in  the  atmosphere  and  rapidly  develop 
when  they  fall  upon  any  nutritive  medium. 

Ropy  Milk. — This  condition  is  caused  by  a  special  bacillus, 
and  is  usually  seen  during  moist  warm  weather.  The  milk 
when  drawn  may  not  show  any  unusual  properties,  but  in  a 
few  hours  becomes  so  viscid  that  a  spoonful  of  it  may  be 
lifted  several  inches  without  breaking  the  connection  between 
the  two  portions. 

CONDENSED  MILK 

The  form  of  condensed  milk  called  "  evaporated  cream  "  con- 
sists merely  of  whole  milk  concentrated  to  about  two-fifths 
of  its  bulk,  but  most  condensed  milks  contain  a  considerable 
amount  of  cane-sugar.  These  samples  represent,  usually, 
wHole  milk  concentrated  to  about  one-third  or  two-sevenths 
of  its  original  volume.  A  small  amount  of  invert-sugar  may 
be  present.  Portions  of  the  lactose  may  crystallize  from  con- 
densed milk,  and  when  solutions  are  prepared  for  analysis, 
abnormal  polarimetric  reading  will  result  unless  the  liquid 
stands  for  some  hours  or  is  heated  for  a  short  time  to  100°. 
The  most  common  defect  in  condensed  milks  is  deficiency  in 
fat,  due  to  preparation  from  closely-skimmed  milks.  Preser- 
vatives (other  than  cane-sugar)  and  coloring- matters  are  rarely, 
if  ever,  used,  nor  is  it  likely  that  foreign  fats  will  be  present. 

ANALYSES  OF  COMMERCIAL  CONDENSED  MILKS 


TOTAL 
SOLIDS. 

FAT. 

PROTEIDS. 

LACTOSE. 

SUCROSE. 

ASH. 

ANALYST. 

36.7 

10.5 

9-7 

14.2 

none 

2.1 

Pearmain  and  Moor 

31.2 

9.6 

9.2 

10.9 

none 

i-S 

F.  J.  Aschman 

28.1 

8.8 

8.5 

9.8 

none 

1.8 

F.  J.  Aschman 

78.4 

93 

9.1 

13-4 

40.4 

2.0 

F.  J.  Aschman 

74.2 

9.0 

9-3 

10.2 

43-7 

1-9 

F.  J.  Aschman 

70.9 

1.4 

11.4 

I4.6 

41.9 

1.6 

Pearmain  and  Moor 

The  sucrose  in  the  last  sample  was  determined  by  difference. 


226  FOOD    ANALYSIS 

The  analysis  of  unsweetened  condensed  milks  is  conducted 
as  with  ordinary  milk,  the  sample  having  been  previously 
diluted  with  several  times  its  weight  of  water  heated  to  boil- 
ing, cooled,  and  made  up  to  a  definite  volume.  The  fat  may 
be  readily  estimated  by  the  L-B.  process. 

The  full  analysis  of  sweetened  condensed  milk  is  difficult, 
and  many  of  the  published  figures  are  probably  erroneous. 
The  large  amount  of  cane-sugar  interferes  with  the  extraction 
of  the  fat  by  solvents.  The  same  difficulty  occurs  in  the 
analysis  of  some  prepared  infant-foods,  such  as  mixtures  of 
milk  with  malt  and  glucose. 

For  the  general  operations,  a  portion  of  the  well-mixed 
contents  of  a  freshly-opened  can  should  be  accurately 
weighed,  diluted  with  a  known  amount  of  water,  and  well 
mixed,  from  which  mass  the  portions  for  analysis  may  be 
taken  and  the  results  calculated  to  the  original  sample.  50 
grams  mixed  with  100  c.c.  of  water  will  be  a  convenient 
quantity.  For  the  polarimetric  determination  of  lactose,  a 
special  procedure  will  be  necessary  ;  but  for  determination  of 
solids,  ash,  total  proteids,  and  total  reducing  sugars,  the  ex- 
amination may  be  made  as  with  ordinary  milk  upon  this 
diluted  sample. 

Fat. — The  Adams  method  is  usually  employed.  J.  F. 
Geisler  has  investigated  its  application  to  condensed  milks 
and  devised  the  following  method  :  A  quantity  of  the  dilute 
solution  equal  to  not  more  than  I  gram  of  the  sample  is  dis- 
tributed on  a  fat-free  paper  coil  as  described  on  page  203  .and 
extracted  for  five  hours  writh  petroleum  spirit  or  a  mixture  of 
petroleum  spirit  and  anhydrous  ether  containing  I  5  per  cent, 
of  the  latter. 

The  Werner-Schmid  method  may  be  employed,  but  the  fat 
is  apt  to  be  contaminated  with  caramel.  It  should  be  dissolved 
in  anhydrous  ether,  by  which  the  caramel  will  be  left  adher- 
ing to  the  glass  ;  and  after  washing  this  with  a  little  more 


CONDENSED     MILK 

ether,  it  should  be  dried  and  weighed  and  the  fat  determined 
by  difference. 

The  estimation  of  fat  by  centrifugal  method  is  seriously 
impeded  by  the  carbonization  of  the  sucrose,  and  various 
methods  have  been  proposed  for  overcoming  this  difficulty. 
A.  E.  Leach  devised  the  following  method,  which  he  finds  to 
be  more  trustworthy  than  ordinary  extractions  with  solvents. 
Leach  applied  the  process  to  a  centrifugal  method  not  identical 
with  the  one  described  on  page  206,  but  this  is  not  important : 

15  c.c.  of  diluted  material  are  measured  into  the  test-bottle, 
water  added  sufficient  to  fill  it  to  the  beginning  of  the  stem, 
and  then  4  c.c.  of  the  copper  sulfate  solution  used  for  sugar 
determination,  the  mixture  shaken  well,  and  the  precipitate 
settled  by  whirling  the  bottle  in  the  machine.  The  super- 
natant liquid  is  drawn  off  with  a  slender-stemmed  pipet  the 
opening  of  which  is  covered  with  a  small  piece  of  absorbent 
cotton.  On  withdrawing  the  pipet  this  cotton  is  dislodged  by 
pressing  it  against  the  neck  so  that  it  remains  in  the  bottle. 
The  precipitate  is  washed  twice  with  water  by  the  same 
method,  settling  the  precipitate  in  each  case  by  the  use  of  the 
centrifuge,  taking  care  that  the  mass  is  well  stirred  with  the 
water  in  each  operation.  After  the  second  washing,  about 
15  c.c.  of  water  are  put  in,  the  precipitate  stirred  up,  the 
amyl  alcohol  mixture  added,  then  the  sulfuric  acid,  as  directed 
on  page  206,  the  mixture  whirled,  and  the  fat  measured.  The 
percentage  of  fat  will  be  that  based  on  the  15  c.c.  used,  and 
the  amount  in  the  original  sample  may  be  calculated  from  the 
dilution. 

Sugars. — If  regard  is  to  be  given  to  the  presence  of  invert- 
sugar,  a  special  method  must  be  followed.  The  processes  first 
given  consider  lactose  and  sucrose  only. 

Lactose. — The  heating  employed  in  the  manufacture  of  con- 
densed milk  may  reduce  the  rotatory  power  of  the  sugar 
sufficiently  to  cause  error  in  the  polarimetric  method.  The 


228  FOOD    ANALYSIS 

reducing  power  with  alkaline  copper  solutions  is  not  seriously 
affected. 

Sucrose. — This  determination  may  be  made  by  difference  ; 
that  is,  subtracting  the  sum  of  the  other  ingredients  from 
the  total  solids.  This  will  serve  for  ordinary  inspection  pur- 
poses, since  the  amount  present  is  almost  always  large,  gen- 
erally more  than  the  total  of  milk-solids,  and  an  error  even  of 
several  per  cent,  does  not  affect  the  judgment  as  to  the 
wholesomeness  of  the  sample.  Exact  work  requires,  how- 
ever, that  the  cane-sugar  be  determined  directly,  and  several 
processes  have  been  devised  for  the  purpose.  Sucrose  exerts 
but  little  action  on  Fehling's  solution,  but  invert-sugar  acts 
powerfully,  and  some  processes  depend  on  determining  the 
reducing  power  before  and  after  inversion.  Since  the  polari- 
metric  reading  is  also  markedly  changed  by  the  inversion,  the 
difference  in  polarization  may  be  employed.  Processes  of 
fermentation  may  be  so  conducted  as  to  remove  the  sucrose 
(also  any  form  of  glucose)  while  the  lactose  is  unaffected. 
This  method  is  chiefly  valuable  for  recognizing  invert-sugar 
or  either  of  its  constituents. 

When  inversion  methods  are  used,  they  must  be  such  as  to 
secure  prompt  inversion  of  the  sucrose  without  affecting  the 
lactose.  Experiment  shows  that  citric  acid  and  invertase  are 
the  most  suitable  agents.  A.  W.  Stokes  and  R.  Bodmer  have 
worked  out  the  citric  acid  method  substantially  as  follows  : 

25  c.c.  of  the  diluted  sample  are  coagulated  by  addition  of 
I  per  cent,  of  citric  acid,  without  heating,  and  made  up  to 
200  c.c.  plus  the  volume  of  the  precipitated  fat  and  proteids  (see 
p.  214).  The  liquid  portion,  which  now  measures  200  c.c.,  is 
passed  through  a  dry  filter.  The  reducing  power  with  alka- 
line copper  solutions  is  determined  at  once  upon  50  c.c.  of 
this  filtrate.  To  another  50  c.c.,  I  per  cent,  of  citric  acid 
is  added  and  the  solution  boiled  for  10  minutes  and  the 
reducing  power  also  determined.  The  increase  over  that  of 


CONDENSED     MILK  22Q 

the  first  solution  is  due  to  the  invert-sugar  formed  by  the 
action  of  the  citric  acid  on  the  sucrose.  It  is  necessary  to 
bear  in  mind  that  the  reducing  equivalents  of  lactose  and 
invert-sugar  are  not  the  same.  If  a  volumetric  method  be 
employed,  it  is  probable  that  the  Gerrard-Allen  method 
(page  1 1 8)  will  be  satisfactory. 

The  following  method  is  based  on  the  difference  in  polari- 
metric  reading  before  and  after  action  of  invertase.  About 
75  grams  of  the  sample  are  accurately  weighed  in  a  100  c.c. 
flask,  diluted  to  about  80  c.c.,  heated  to  boiling,  cooled,  and 
7.5  c.c.  of  acid  mercuric  nitrate  solution  added.  The  mixture 
is  made  up  to  100  c.c.,  well  shaken,  filtered  through  a  dry 
filter,  and  the  polarimetric  reading  taken  at  once.  It  will  be 
the  sum  of  the  effect  of  the  two  sugars.  The  volume  of  the 
sugar-containing  liquid  is  calculated  by  allowing  for  the  pre- 
cipitated proteids  and  fat,  as  described  on  page  214. 

50  c.c.  of  the  filtrate  are  placed  in  a  flask  marked  at  5  5  c.c., 
a  piece  of  „ litmus  paper  dropped  in,  and  the  excess  of  nitric 
acid  cautiously  neutralized  by  sodium  hydroxid  solution. 
The  liquid  is  then  faintly  acidified  by  a  single  drop  of  acetic 
acid  (it  must  not  be  alkaline),  a  few  drops  of  an  alcoholic 
solution  of  thymol  are  added,  and  then  2  c.c.  of  a  solution  of 
invertase,  prepared  by  grinding  half  a  cake  of  ordinary  com- 
pressed yeast  with  10  c.c.  of  water  and  filtering.  The  flask  is 
corked  and  allowed  to  remain  at  a  temperature  of  35°  to  40° 
for  24  hours.  The  cane-sugar  will  be  inverted,  while  the 
milk-sugar  will  be  unaffected.  The  flask  is  filled  to  the  mark 
(55  c.c.)  with  washed  aluminum  hydroxid  and  water,  mixed, 
filtered,  and  the  polarimetric  reading  taken.  The  amount  of 
cane-sugar  can  be  determined  from  the  difference  in  the  two 
readings  by  the  formula  on  page  125. 

A  powerful  solution  of  invertase  may  be  prepared  by  the 
method  recommended  by  O'Sullivan  and  Tompson.  Brewer's 
yeast  is  allowed  to  stand  at  a  temperature  of  1 5°  for  a  month. 


230  FOOD    ANALYSIS 

The  liquid  is  filtered  and  sufficient  alcohol  added  to  give 
about  12  per  cent,  of  absolute  alcohol.  After  a  few  days  the 
liquid  is  filtered  and  is  ready  for  use.  The  alcohol  acts  as  a 
preservative. 

W.  D.  Bigelow  and  K.  P.  McElroy  propose  the  following 
routine  method  for  the  determination  of  the  sugars,  including 
invert-sugar,  in  condensed  milk.  The  solutions  used  are  : 

Acid  Mercuric  lodid. — Mercuric  chlorid,  1.35  grams;  potas- 
sium iodid,  3.32  grams;  glacial  acetic  acid,  2  c.c.  ;  water, 
64  c.c. 

Alumina-cream. — See  page  123. 

The  entire  contents  of  the  can  are  transferred  to  a  porcelain 
dish  and  thoroughly  mixed.  A  number  of  portions  of  about 
25  grams  are  weighed  carefully  in  100  c.c.  flasks.  Water  is 
added  to  two  of  the  portions,  and  the  solutions  boiled.  The 
flasks  are  then  cooled,  clarified  by  means  of  a  small  amount 
of  the  acid  mercuric  iodid  and  alumina-cream,  made  up  to 
mark,  filtered,  and  the  polarimetric  reading  noted.  Other 
portions  of  the  milk  are  heated  in  the  water-bath  to  55°  ;  one- 
half  of  a  cake  of  compressed  yeast  is  added  to  each  flask  and 
the  temperature  maintained  at  55°  for  five  hours.  Acid  mer- 
curic iodid  and  alumina-cream  are  then  added,  the  solution 
cooled  to  room  temperature,  made  up  to  mark,  mixed,  fil- 
tered, and  polarized.  The  amount  of  cane-sugar  is  deter- 
mined by  formula  on  page  125.  Correction  for  the  volume  of 
precipitated  solids  may  be  made  by  the  double-dilution 
method  (p.  30).  The  total  reducing  sugar  is  estimated 'in 
one  of  the  portions  by  one  of  the  reducing  methods,  and  if 
the  sum  of  it  and  the  amount  of  cane-sugar  obtained  by  in- 
version is  equal  to  that  obtained  by  the  direct  reading  of  both 
sugars  before  inversion,  no  invert-sugar  is  present.  If  the 
amount  of  reducing  sugar  seems  to  be  too  great,  the  milk- 
sugar  must  be  re-determined  as  follows  :  250  grams  of  the 
condensed  milk  are  dissolved  in  water,  the  solution  boiled, 


BUTTER  231 

cooled  to  80°,  a  solution  of  about  4  grams  of  glacial  phos- 
phoric acid  added,  the  mixture  kept  at  80°  for  a  few  minutes, 
then  cooled  to  room  temperature,  made  up  to  mark,  shaken, 
and  filtered.  It  may  be  assumed  that  the  volume  of  the  pre- 
cipitate is  equal  to  that  obtained  by  mercuric  iodid  solution. 
Enough  sodium  hydroxid  is  then  added  to  not  quite  neutral- 
ize the  free  acid,  and  sufficient  water  to  make  up  for  the  vol- 
ume of  the  solids  precipitated  by  the  phosphoric  acid.  The 
mixture  is  then  filtered  and  the  filtrate  is  measured  in  portions 
of  100  c.c.  into  200  c.c.  flasks.  A  solution  containing  20 
milligrams  of  potassium  fluorid  and  half  a  cake  of  compressed 
yeast  is  added  to  each  flask,  and  the  mixture  allowed  to  stand 
for  10  days  at  a  temperature  between  25°  and  30°.  The 
invert-sugar  and  cane-sugar  are  fermented  and  removed  by 
the  yeast  in  the  presence  of  a  fluorid,  while  milk-sugar  is 
unaffected.  The  flasks  are  filled  to  the  mark  and  the  milk- 
sugar  determined  either  by  reducing  or  by  the  polariscope. 
The  amount  of  copper  solution  reduced  by  the  lactose  and 
invert-sugar,  less  the  equivalent  of  lactose  remaining  after 
fermentation,  is  due  to  invert-sugar. 


BUTTER 

Butter  is  a  mixture  of  fat,  water,  and  curd.  The  water  contains 
milk-sugar  and  the  salts  of  the  milk.  Common  salt  is  usually 
present,  being  added  after  the  churning.  Artificial  coloring 
is  frequently  used. 

Butter-fat  is  distinguished  from  other  animal  fats  in  that  it 
contains  a  notable  proportion  of  acid  radicles  with  a  small 
number  of  carbon  atoms.  Thus,  about  91  per  cent,  consists 
of  palmitin  and  olein  and  the  remainder  of  butyrin  and  ca- 
proin,  along  with  small  amounts  of  caprylin,  caprin,  myristin, 
and  some  others.  According  to  the  experiments  of  Hehner 
and  Mitchell,  stearin  is  present  only  in  very  small  quantity. 
The  exact  arrangement  of  these  constituents  is  unknown. 


232  FOOD    ANALYSIS 

The  composition  of  commercial  butter  usually  varies  within 
the  following  limits  : 

Fat, .    .  78  per  cent,  to  94  per  cent. 

Curd, I        "          "3         " 

Water,      5        "          "14         " 

Salt, o        "          "7         " 

Batter  containing  over  40  per  cent,  of  water  is  sometimes 
sold.  Such  samples  are  pale  and  spongy,  lose  weight,  and 
become  rancid  rapidly. 

The  official  methods  of  the  A.  O.  A.  C.  for  the  analysis  of 
butter  are  as  follows  : 

Preparation  of  the  Sample. — If  large  quantities  of  butter 
are  to  be  sampled,  a  butter  trier  or  sampler  may  be  used. 
The  portions  thus  drawn,  about  500  grams,  are  to  be  per- 
fectly melted  in  a  closed  vessel  at  as  low  a  temperature  as 
possible,  and  when  melted  the  whole  is  to  be  shaken  violently 
for  some  minutes  until  the  mass  is  homogeneous  and  suffici- 
ently solidified  to  prevent  the  separation  of  the  water  and  fat. 
A  portion  is  then  poured  into  the  vessel  from  which  it  is  to  be 
weighed  for  analysis,  and  should  nearly  or  quite  fill  it.  This 
sample  should  be  kept  in  a  cold  place  till  analyzed. 

Water. — From  1.5  to  2.5  grams  are  dried  to  constant 
weight  at  the  temperature  of  boiling  water,  in  a  dish  with  flat 
bottom,  having  a  surface  of  at  least  20  sq.  cm.  The  use  of 
clean  dry  sand  or  asbestos  with  the  butter  is  admissible,  and  is 
necessary  if  a  dish  with  round  bottom  be  employed. 

Fat. — The  dry  butter  from  the  water  determination  is  dis- 
solved in  the  dish  with  absolute  ether  or  with  petroleum 
spirit  (sp.  gr.  0.680).  The  contents  of  the  dish  are  then 
transferred  to  a  weighed  Gooch  crucible  with  the  aid  of  a 
wash-bottle  filled  with  the  solvent,  and  are  washed  until  free 
from  fat.  The  crucible  and  contents  are  heated  at  the  tem- 
perature of  boiling  water  till  the  weight  is  constant. 


BUTTER  ^*55fc  233 


The  fat  may  also  be  determined  by  drying  the  butter  on 
asbestos  or  sand,  and  extracting  by  anhydrous  alcohol-free 
ether.  After  evaporation  of  the  ether  the  extract  is  heated 
to  constant  weight  at  the  temperature  of  boiling  water  and 
weighed. 

Casein,  Ash,  and  Chlorin. — The  crucible  containing  the 
residue  from  the  fat  determination  is  covered  and  heated, 
gently  at  first,  gradually  raising  the  temperature  to  just  below 
redness.  The  cover  is  removed  and  the  heat  continued  until 
the  material  is  white.  The  loss  in  weight  represents  casein, 
and  the  residue  mineral  matter.  In  this  mineral  matter  dis- 
solved in  water  slightly  acidulated  with  nitric  acid,  chlorin 
may  be  determined  gravimetrically  with  silver  nitrate,  or,  after 
neutralization  with  calcium  carbonate,  volumetrically,  using 
potassium  chromate  as  indicator. 

Salt. — About  10  grams  are  weighed  in  a  beaker  in  por- 
tions of  about  I  gram  at  a  time  taken  from  different  parts  of 
the  sample.  Hot  water  (about  20  c.c.)  is  now  added  to  the 
beaker,  and  after  the  butter  has  melted,  the  mass  is  poured 
into  the  bulb  of  a  separating  funnel,  which  is  then  closed  and 
shaken  for  a  few  moments.  After  standing  until  the  fat  has 
all  collected,  the  water  is  allowed  to  run  into  an  Erlenmeyer 
flask,  with  care  not  to  let  fat  globules  pass.  Hot  water  is 
again  added  to  the  beaker,  and  the  extraction  is  repeated  from 
ten  to  fifteen  times,  using  each  time  from  10  to  20  c.c.  of 
water.  The  resulting  washings  contain  all  but  a  mere  trace 
of  the  salt  originally  present  in  the  butter.  The  chlorin  is 
determined  volumetrically  in  the  filtrate  by  means  of  standard 
silver  nitrate  and  potassium  chromate  indicator  and  calculated 
to  sodium  chlorid. 

Adulteration  with  Foreign  Fats. — The  chief  adulteration  of 
butter  consists  in  the  substitution  of  foreign  fats,  especially  the 
product  known  as  oleomargarin. 

When  fats  are  saponified  and  the  soap  treated  with  acid,  the 


234  FOOD    ANALYSIS 

individual  fatty  acids  are  obtained.  It  is  upon  the  recognition 
of  the  peculiar  acid  radicles  existing  in  butter  that  the  most 
satisfactory  method  of  distinguishing  it  from  other  fats  is 
based.  Since  the  relative  proportion  of  these  radicles  differs 
in  different  samples,  the  quantitative  estimation  cannot  be  made 
with  accuracy ;  but  when  the  foreign  fats  are  substituted  to 
the  extent  of  20  per  cent,  or  more,  the  adulteration  can  be 
detected  with  certainty  and  an  approximate  quantitative  deter- 
mination made. 

The  detection  of  adulteration  of  butter-fat  by  other  fats  is 
generally  carried  out  by  the  determination  of  the  volatile  acid, 
but  some  other  confirmatory  processes  are  occasionally  em- 
ployed. The  data  for  interpreting  results  will  be  found  in  the 
table  on  page  168. 

Volatile  Acids. — The  glycerol-soda  method  (page  146)  is 
sufficient  for  the  purpose.  No  advantage  will  result  from 
using  the  tedious  method  with  alcoholic  solution  ;  indeed, 
under  ordinary  circumstances  the  latter  is  probably  less  accu- 
rate. 

Butter  (5  grams)  yields  a  distillate  requiring  from  24  to  34 
c.c.  of  decinormal  alkali.  Several  instances  have  been  pub- 
lished in  which  genuine  butter  has  given  a  figure  as  low  as 
22.5  c.c.,  but  such  results  are  uncommon.  The  materials 
employed  in  the  preparation  of  oleomargarin  yield  a  distillate 
requiring  less  than  I  c.c.  of  alkali.  Commercial  oleomargarin 
is  usually  churned  with  milk  in  order  to  secure  a  butter 
flavor,  and,  thus  acquiring  a  small  amount  of  butter-fat, 
yields  distillates  capable  of  neutralizing  from  I  to  2  c.c.  of 
alkali.  , 

If  coconut  oil  (see  page  168)  has  been  used  in  the  prepara- 
tion of  the  oleomargarin,  the  figure  will  be  higher,  but  there 
will  still  be  no  difficulty  in  distinguishing  pure  butter. 

Saponification  Value. — In  the  absence  of  coconut  oil,  the 
saponification  value  will  give  valuable  indications  as  to  the 


BUTTER  235 

purity  of  a  butter  sample.  It  is  possible  to  make  oleomar- 
garin, by  the  addition  of  coconut  oil,  which  would  have  the 
same  saponification  value  as  pure  butter. 

Specific  Gravity. — According  to  Skalweit,  the  greatest 
differences  between  the  specific  gravity  of  butter  and  its 
adulterants  are  found  at  a  temperature  of  35°,  but  the  deter- 
mination is  more  conveniently  made  at  the  temperature  of 
boiling  water.  The  Sprengel  tube  or  Westphal  balance  may 
be  employed  for  the  purpose. 

The  determination  of  the  Reichert  number  will  usually  give 
sufficient  information  as  to  the  nature  of  a  butter  sample.  In 
doubtful  cases  it  may  be  of  advantage  to  apply  other  tests  as 
corroborative  evidence.  The  determination  of  soluble  and 
insoluble  acids  may  be  employed,  but  Valenta's  test  and  the 
refractometric  examination  are  especially  mentioned  as  fur- 
nishing results  with  little  trouble  in  a  short  time. 

Soluble  and  Insoluble  Acids. — The  proportion  of  insoluble 
acids  in  butter  is  usually  about  87.5  per  cent,  and  of  soluble 
acids,  calculated  as  butyric,  about  5  per  cent.  The  insoluble 
acids  may  be  present  to  the  extent  of  88.5  per  cent.,  but, 
according  to  most  authorities,  they  will  only  reach  90  per 
cent,  in  the  presence  of  adulterants.  These  figures  apply  to 
fresh  samples.  After  keeping  until  rancidity  has  developed 
the  proportion  of  insoluble  acids  may  be  increased  I  per  cent, 
or  more. 

Mixtures  of  butter,  oleomargarin,  and  coconut  oil  may  have 
the  same  proportion  of  insoluble  acids  as  butter. 

Valenta's  Test. — Jones  recommends  the  employment  of  a 
standard  butter  with  which  to  standardize  each  fresh  batch  of 
acid,  and  dilution  of  the  acid  to  such  a  point  that  the  turbidity 
temperature  with  this  butter-fat  is  60°  In  this  way  the  results 
are  comparable  with  those  of  previous  tests. 

With  such  acid  oleomargarin  gave  temperatures  from  95° 
to  1 06°,  and  generally  from  100°  to  102°. 


236  FOOD    ANALYSIS 

Refrac  tome  trie  Examination. — This  is  most  satisfactorily 
made  by  the  oleorefractometer  or  the  butyrorefractometer. 
F.  Jean  prepares  the  sample  for  examination  in  the  former  as 
follows  :  30  grams  of  butter  are  melted  in  a  porcelain  dish  at 
a  temperature  not  exceeding  50°,  stirred  well  with  a  pinch  or 
two  of  gypsum,  and  allowed  to  settle  out  at  the  same  temper- 
ature. The  supernatant  fat  is  decanted  through  a  hot-water 
funnel  plugged  with  cotton  and  poured  while  warm  into  the 
prism  of  the  apparatus,  stirred  with  the  thermometer  until  the 
fat  has  cooled  to  45°,  and  the  deviation  observed.  Ether  must 
not  be  used  for  the  solvent,  as  minute  traces  of  it  seriously 
influence  the  result. 

The  following  table  is  a  summary  of  the  results  obtained 
by  several  observers,  including  F.  Jean  and  T.  M.  Pearmain  : 

DEGREES  IN 
OLEOREFRACTOMETER. 

Butter, —25  to  — 34,  usually  — 30 

Oleomargarin, — 13  to — 18 

Butter  with  lop.  c.  oleomargarin  ( — 17),  .  — 28 
Butter  with  50  p.  c.  oleomargarin,    .    .    .  — 23 

Lard, — 8  to — 14 

Coconut  oil,      ....  — 59 

Arachis  oil,       , 3.5  to  7 

Cottonseed  oil, 12  to  23 

Cottonseed  "  stearin," 25 

De  Bruyn  found  as  low  as  — 2 1  in  butter  from  animals  fed 
on  linseed  cakes.  A  mixture  of  coconut  oil  and  oleomargarin 
may  be  made  having  the  same  refractive  power  as  pure  butter 
Evidently,  therefore,  it  is  not  possible  from  this  datum  alone 
to  state  that  a  given  sample  is  pure  butter,  but  a  sample  ex- 
hibiting a  refraction  of  — 20°  or  under  may  be  pronounced 
adulterated. 

The  results  obtained  by  examination  in  Zeiss's  butyrore- 
fractometer are  in  the  main  the  same  as  those  just  given. 
The  instrument  is  said  to  be  superior  to  the  oleorefractometer, 
and  is  less  costly. 

Commercial  forms  of  oleomargarin  and  butter  exhibit  char- 


BUTTER  237 

acteristic  differences  on  heating,  which  may  be  utilized  for 
rapidly  sorting  a  collection  of  samples.  When  butter  is 
heated  in  a  small  tin  dish  directly  over  a  gas  flame,  it  melts 
quietly,  foams,  and  may  run  over  the  dish.  Oleomargarin, 
under  the  same  conditions,  sputters  noisily  as  soon  as  heated 
and  foams  but  little.  Even  mixtures  of  butter  and  other  fats 
show  this  sputtering  action  to  a  considerable  extent.  The 
effect  depends  upon  the  condition  in  which  the  admixed  Avater 
exists,  and  the  test  is  not  applicable  to  butter  which  has  been 
melted  and  reworked  (renovated  or  process  butter). 

An  alcoholic  solution  of  sodium  hydroxid,  heated  for  a 
moment  with  butter,  and  then  emptied  into  cold  water,  gives 
a  distinct  odor  of  pineapples,  while  oleomargarin  gives  only 
the  alcoholic  odor. 

Butter  Colors. — Most  of  the  butter  and  practically  all  but- 
ter substitutes  are  colored  either  with  preparations  of  turmeric 
and  annatto  or  azo-colors  allied  to  methyl-orange.  The  lat- 
ter forms  are  now  most  largely  used.  They  may  be  detected 
by  the  test  devised  by  J.  F.  Geisler.26  A  small  amount  of 
the  sample,  or,  better,  the  fat  filtered  from  it,  is  mixed  on  a 
porcelain  plate  with  a  little  fuller's  earth.  Azo-colors  give 
promptly  a  red  mass,  while  if  they  are  not  present,  the  mix- 
ture becomes  only  yellow  or  light  brown.  All  samples  of 
fuller's  earth  are  not  equally  active,  and  tests  should  be  made 
with  different  samples  by  using  fat  known  to  contain  the  azo- 
compound  until  a  good  specimen  of  the  earth  is  secured. 

The  precipitate  obtained  by  Geisler  by  mixing  fuller's  earth 
with  a  sample  of  highly  colored  butter  was  washed  with  light 
petroleum  to  remove  the  fat  and  gave  a  violet-red  powder  on 
drying.  Alcohol  immediately  decolorized  it,  but  the  color 
reappeared  on  evaporation  of  the  alcohol.  Boiling  alcohol 
extracted  the  color  from  the  earth,  producing  a  yellow  solu- 
tion. The  color  so  extracted  dissolved  in  sulfuric  acid  to  a 


238  FOOD    ANALYSIS 

yellow  solution,  which,  on  dilution,  developed  a  bright  pink 
or  red  color. 

For  the  detection  of  very  minute  quantities  of  the  color,  the 
sample  may  be  dissolved  in  light  petroleum,  and  the  fuller's 
earth  added  to  the  solution,  when  the  pink  color  will  appear 
as  a  .distinct  ring  or  zone  at  the  edge  of  the  deposited  layer  of 
the  reagent. 

According  to  Geisler,  the  yellow  azo-dye  is  generally  used 
in  conjunction  with  an  orange  variety  which  does  not  respond 
to  the  above  test. 

A.  H.  Low  has  proposed  the  following  test  for  the  yellow 
azo-color  :  A  few  cubic  centimeters  of  the  filtered  fat  are 
mixed  in  a  large  test-tube  with  an  equal  volume  of  a  mixture 
of  one  part  strong  sulfuric  acid  and  four  parts  glacial  acetic 
acid.  The  contents  of  the  tube  are  then  heated  almost  to 
boiling  and  thoroughly  mixed  by  violently  agitating  the  bot- 
tom of  the  tube.  When  now  allowed  to  stand  and  separate, 
the  lower  layer  of  mixed  acids  will  be  strongly  colored 
wine-red  if  the  azo-color  be  present.  Pure  butter-fat  imparts 
no  color  to  the  acids,  or,  at  most,  only  a  faint  brownish 
tinge. 

For  turmeric  and  annatto  mixtures,  E.  W.  Martin's  test 
will  usually  be  satisfactory  :  2  c.c.  carbon  disulfid  are  mixed 
with  I  5  c.c.  of  alcohol,  by  adding  small  portions  of  the  disul- 
fid to  the  alcohol  and  shaking  gently  ;  5  grams  of  the  butter- 
fat  are  added  to  this  mixture  in  a  test-tube  and  shaken.  The 
disulfid  falls  to  the  bottom  of  the  tube,  carrying  with-  it  the 
fatty  matter,  while  any  artificial  coloring-matter  remains  in 
the  alcohol.  The  separation  takes  place  in  from  one  to  three 
minutes.  If  the  amount  of  the  coloring-matter  is  small, 
more  of  the  fat  may  be  used.  If  the  alcoholic  solution  be 
evaporated  to  dryness  and  the  residue  treated  with  concen- 
trated sulfuric  acid,  annatto  will  be  indicated  by  the  produc- 
tion of  a  greenish-blue  color.  With  many  samples  of  oleo- 


f  CHEESE  239 

margarin  a  pink  tint  will  be  obtained,  which  indicates  an 
azo-color. 

Presen>atives. — The  preservatives  used  in  milk  may  be 
found  in  limited  amount  in  butter,  but  boric  acid  is  now 
sometimes  added  as  a  substitute  for  salt.  It  will  be  detected 
by  the  method  given  on  page  89  in  the  water  obtained  by 
melting  the  butter  and  allowing  the  mass  to  settle. 

Glucose2  7  is  now  used  as  a  preservative,  especially  in  butter 
intended  for  export  to  tropical  countries.  C.  A.  Crampton 
found  as  much  as  10  per  cent,  in  a  sample  of  Beurre  rouge  (a 
highly  colored  butter)  intended  for  exportation  to  Guadeloupe. 
For  the  detection  of  glucose  the  phenylhydrazin  test  might  be 
used.  For  determination  of  glucose,  Crampton  used  the  fol- 
lowing method  :  10  grams  of  the  sample  were  washed  with 
successive  portions  of  convenient  bulk,  the  solution  made  up 
to  250  c.c.,  and  an  aliquot  portion  determined,  as  given  on  page 
1 1 6.  The  solution  may  also  be  clarified  by  alumina-cream  or 
acid  mercuric  nitrate  and  examined  in  the  polarimeter. 


CHEESE 

Cheese  is  the  curd  of  milk  which  has  been  separated  from 
it,  pressed,  and  undergone  some  fermentation.  The  precipita- 
tion is  produced  either  by  allowing  the  milk  to  become  sour 
— when  the  lactic  acid  is  the  agent — or  by  rennet.  The  first- 
named  method  is  mainly  applied  to  the  manufacture  of  so- 
called  Dutch  or  sour-milk  cheese,  green  Swiss  cheese,  and 
cottage  cheese.  More  commonly  cheese  is  obtained  by  means 
of  rennet  derived  from  the  fourth  stomach  of  the  calf.  The 
action  is  due  to  an  enzym  which  acts  directly  on  the  proteids 
and  does  not  produce  its  effect  through  the  intervention  of 
acids.  The  curd  (cheese)  undergoes,  by  keeping,  various 
decompositions,  some  essentially  putrefactive,  and  due  to  the 


24O  FOOD    ANALYSIS 

action-  of  microbes.  The  decomposition  of  the  cheese  is 
termed  ''ripening." 

In  the  sour-milk  cheeses,  ripening  is  restricted  intention- 
ally, since  there  is  liability  to  an  irregular  and  miscellaneous 
bacterial  growth  by  which  the  fermentations  may  be  carried 
too  far,  undesirable  and  even  harmful  products  being  formed. 
Such  cheeses  are  intended  for  prompt  use. 

Cheese  contains  no  casein,  if  by  this  term  is  meant  the 
proteid  as  it  exists  in  milk,  or  when  precipitated  from  milk  by 
acids.  When  milk  is  coagulated  by  rennet,  only  a  part  of  the 
proteids  enter  into  the  curd;  true  casein  contains  about  15.7 
per  cent,  of  nitrogen,  but  the  proteid  matter  of  cheese  con- 
tains about  14.3  per  cent.  Under  the  process  of  ripening 
this  is  further  decomposed,  amido-  and  ammonium  com- 
pounds, peptones  and  albumoses,  being  formed. 

The  following  figures,  obtained  by  L.  L.  Van  Slyke,  will 
serve  to  give  some  idea  of  the  extent  to  which  the  curd  is 
changed  in  ripening.  The  figures  represent  average  percent- 
age on  the  total  nitrogen.  The  cheese  was  an  American 
cheddar : 

GREEN  CHEESE.    AFTER  FIVE  MONTHS. 

Soluble  nitrogen  compounds,      .    .    .4.23  35- 5 2 

"       amido  "  ...  none  u.66 

"       ammonium      "  ...  none  2.92 

Van  Slyke's  experiments  seem  also  to  indicate  that  the 
cheese  ripened  more  rapidly  when  the  curd  was  precipitated 
by  a  larger  quantity  of  rennet  and,  especially,  that  cheese  rich 
in  fat  ripened  more  rapidly  than  skim-milk  cheese. 

In  addition  to  the  fat  and  nitrogenous  compounds  just 
mentioned,  cheese  may  contain  a  small  amount  of  milk-sugar 
and  of  lactic  and  other  organic  acids.  There  is  present  also 
a  certain  proportion  of  mineral  matter,  alkaline  and  earthy 
phosphates,  along  with  any  salt  that  has  been  added.  Traces 
of  nitrates  have  been  found. 


CHEESE  241 

Skimmed  milk  is  not  infrequently  used  for  the  production 
of  cheese.  Partially- skimmed  milk  is  used  in  the  preparation 
of  certain  Dutch  cheeses.  Foreign  fats,  such  as  are  used  in 
the  manufacture  of  oleomargarin,  are  sometimes  incorporated, 
the  article  being  known  as  "  filled  cheese." 

The  ash  of  cheese  consists  largely  of  calcium  phosphate 
and  salt.  G.  Mariani  and  E.  Tasselli  have  estimated  the  total 
ash,  chlorin,  calcium,  and  phosphoric  acid  in  15  samples  of 
cheese.  The  amounts  of  salt  (calculated  from  the  chlorin)  de- 
pend on  the  mode  of  salting.  The  proportion  of  phosphoric 
oxid  was  always  greater  than  that  necessary  to  form  trical- 
cium  phosphate,  ranging  from  1.07  and  1.08  equivalents  of 
phosphoric  anhydrid  to  calcium  oxid  in  cheese  made  from 
sour  milk  to  1.56  to  I  in  Gorgonzola,  1.67  to  I  in  skim-milk 
cheese,  and  1.75  to  I  in  Edam  cheese.  The  largest  quanti- 
ties of  calcium  and  phosphoric  oxid  were  found  in  sheep's- 
milk  cheese  and  in  cheese  made  from  sour  milk,  whence  it 
follows  that  acidity  does  not  prevent  the  precipitation  of  cal- 
cium phosphate  in  the  curds.  The  excess  of  phosphoric  oxid 
obtained  was  attributed  to  acid  phosphates. 

The  salt  in  cheese  usually  ranges  between  I  and  4  per 
cent. 

Analytic  Methods. — The  analytic  points  usually  deter- 
mined in  regard  to  cheese  are  water,  fat,  casein,  ash,  the  pres- 
ence of  fats  other  than  butter-fat,  and  coloring-matters. 

In  addition  to  this,  especially  in  comparing  the  qualities  of 
genuine  cheeses,  the  proportion  of  proteic,  amidic,  and  ammo- 
niacal  nitrogen  is  of  value. 

Care  should  be  taken  to  select  for  analysis  a  sample  which 
represents  the  average  composition  of  the  entire  cheese. 

The  following  methods  for  the  determination  of  water,  fat, 
ash,  total  nitrogen,  and  acidity  have  been  adopted  by  the 
A.  O.  A.  C. : 

Sampling. — When  the  cheese  can  be  cut,  a  narrow  wedge- 

21 


242  FOOD    ANALYSIS 

shaped  segment,  reaching  from  the  outer  edge  to  the  center 
of  the  cheese,  is  taken.  This  is  to  be  cut  into  strips  and 
passed  through  a  sausage-grinding  machine  three  times. 
When  the  cheese  cannot  be  cut,  samples  are  taken  by  a 
cheese  trier.  If  only  one  plug  can  be  obtained,  this  should 
be  perpendicular  to  the  surface,  at  a  point  one-third  of  the 
distance  from  the  edge  to  the  center  of  the  cheese.  The 
plug  should  reach  entirely  through,  or  only  half-way  through, 
the  cheese.  When  possible,  draw  three  plugs — one  from  the 
center,  one  from  a  point  near  the  outer  edge,  and  one  from  a 
point  half-way  between  the  other  two.  For  inspection  pur- 
poses, the  rind  may  be  rejected  ;  but  for  investigations  requir- 
ing the  absolute  amount  of  fat  in  the  cheese,  the  rind  is 
included  in  the  sample.  It  is  preferable  to  grind  the  plugs  in 
a  sausage  machine,  but  when  this  is  not  done,  they  should  be 
cut  very  fine  and  carefully  mixed. 

Water. — Between  2  and  5  grams  of  the  sample  should  be 
placed  in  a  weighed  platinum  or  porcelain  dish  which  con- 
tains a  small  amount  of  material,  such  as  freshly  ignited  as- 
bestos or  sand,  to  absorb  the  fat  which  may  run  out.  This 
is  then  heated  in  a  water-oven  for  10  hours  and  weighed  ;  the 
loss  in  weight  is  considered  as  water.  If  preferred,  the  dish 
may  be  placed  in  a  desiccator  over  concentrated  sulfuric  acid 
and  dried  to  constant  weight,  but  this  may  require  many  days. 
The  acid  should  be  renewed  when  the  cheese  has  become 
nearly  dry. 

Fat. — The  extraction-tube  described  on  page  202  is  prepared 
as  follows  :  Cover  the  perforations  in  the  bottom  of  the  tube 
with  asbestos,  and  on  this  place  a  mixture  containing  equal 
parts  of  anhydrous  copper  sulfate  and  pure  dry  sand  to  the 
depth  of  about  5  cm.,  packing  loosely,  and  cover  the  upper 
surface  with  a  film  of  asbestos.  On  this  are  placed  from  2  to  5 
grams  of  the  sample,  the  mass  extracted  for  5  hours  with  anhy- 
drous ether,  then  removed  and  ground  to  fine  powder  with  pure 


CHEESE  243 

sand  in  a  mortar.  The  mixture  is  placed  in  the  extraction 
tube,  the  mortar  washed  free  from  all  matters  with  ether,  the 
washings  being  added  to  the  tube,  and  the  extraction  is  con- 
tinued for  10  hours.  The  fat  so  obtained  is  dried  at  100°  to 
constant  weight. 

Total  Nitrogen. — This  is  determined  by  the  Kjeldahl-Gun- 
ning  method,  using  2  grams  of  the  sample.  The  percentage, 
multiplied  by  6.25,  gives  the  nitrogen  compounds. 

Ash. — The  dry  residue  from  the  water  determination  may 
be  taken  for  the  ash.  If  the  cheese  be  rich,  the  asbestos  will 
be  saturated  therewith.  This  mass  may  be  ignited  carefully, 
and  the  fat  allowed  to  burn  off,  the  asbestos  acting  as  a  wick. 
No  extra  heating  should  be  applied  during  the  operation,  as 
there  is  danger  of  spurting.  When  the  flame  has  died  out, 
the  burning  may  be  completed  in  a  muffle  at  low  redness. 
When  desired,  the  salt  may  be  determined  in  the  ash  by  titra- 
tion  with  silver  nitrate  and  potassium  chromate. 

Provisional  Method  for  the  Determination  of  the  Acidity  in 
Cheese. — Water  at  a  temperature  of  40°  is  added  to  10  grams 
of  finely  divided  cheese  until  the  volume  equals  105  c.c., 
agitated  vigorously,  and  filtered.  Portions  of  25  c.c.  of  the 
filtrate  corresponding  to  2.5  grams  of  the  cheese  are  titrated 
with  decinormal  solution  of  sodium  hydroxid,  using  phenol- 
phthalein  as  indicator.  The  amount  of  acid  is  expressed  as 
lactic  acid. 

The  above  processes  may  be  advantageously  modified  in 
some  respects.  The  determination  of  water  may  be  made  by 
the  extraction  of  the  cheese  with  alcohol  and  ether  and 
drying  of  the  alcohol-ether  extract  and  fat-free  solids  sep- 
arately. A.  W.  Blyth  recommends  this  method  as  more 
accurate  and  less  tedious  than  the  direct  drying.  In 
the  determination  of  ash,  it  will  be  better  to  extract  the 
charred  mass  with  water  and  proceed  as  described  in  the  de- 
termination of  the  ash  of  milk. 


244  FOOD    ANALYSIS 

The  fat  extracted  by  ether  may  be  examined  for  other  than 
butter-fat  by  the  distillation  method  in  the  usual  way.  When 
the  composition  of  the  fat  is  alone  desired,  it  may  often  be 
extracted  by  simpler  methods.  T.  M.  Pearmain  and  C.  G. 
Moor  recommend  that  50  grams  be  chopped  fine  and  tied  up  in 
a  muslin  bag,  which  is  placed  in  a  water-bath.  When  the 
water  is  heated,  the  fat  will  generally  run  out  clear.  If  not 
clear,  it  can  be  filtered  through  paper. 

O.  Henzold  suggests  the  following :  300  grams  of  the 
powdered  cheese  are  agitated  in  a  wide-neck  flask  with  700 
c.c.  of  5  per  cent,  solution  of  potassium  hydroxid  previously 
warmed  to  20°.  In  about  10  minutes  the  cheese  dissolves, 
the  fat  floats,  and  by  cautious  shaking  may  be  collected  in 
lumps.  The  liquid  is  diluted,  the  fat  removed,  washed  in  very 
cold  water,  kneaded  as  dry  as  possible,  melted,  and  filtered. 
It  is  claimed  that  the  fat  is  not  altered  in  composition  by  the 
process. 

The  fat  of  cheese  may  be  estimated  by  the  centrifugal 
method,  as  follows  : 

About  3  grams  of  the  mixed  cheese  in  small  fragments  are 
weighed  and  transferred  to  the  bottle,  the  last  portions  being 
washed  in  with  the  aid  of  water.  A  few  drops  of  ammonium 
hydroxid  are  added,  and  sufficient  water  to  make  the  liquid 
about  15  c.c.  The  liquid  is  warmed  with  occasional  shaking 
until  the  cheese  is  well  disintegrated,  and  then  treated  as  a 
sample  of  milk.  The  percentage  of  fat  is  found  by  multiply- 
ing the  percentage  reading  by  15.45  and  dividing  by  the  num- 
ber of  grams  of  cheese  taken  for  analysis. 

W.  A.  Chattaway,  T.  M.  Pearmain,  and  C.  G.  Moor  use  the 
following  modification  :  2  grams  of  the  cheese  are  placed  in  a 
small  dish  and  heated  on  the  water-bath  with  30  c.c.  of  con- 
centrated hydrochloric  acid  until  a  dark,  purplish-colored 
solution  is  produced.  The  mixture  is  now  poured  into  the 
test  bottle,  portions  of  solution  remaining  in  the  dish  rinsed 


CHEESE  245 

with  the  hydrochloric  acid  fusel-oil  mixture  into  the  bottle, 
and,  finally,  enough  strong  hot  acid  added  to  fill  the  bottle  up 
to  the  mark.  It  is  then  whirled  for  about  a  minute.  The 
difficulty  in  this  method  is  to  get  all  the  fat  into  the  bottle. 
It  is  best  to  weigh  the  cheese  in  the  bottle. 

Bondzynski  applies  the  Werner-Schmid  method  to  the  de- 
termination of  fat  in  cheese,  as  follows  :  A  weighed  quantity 
of  the  finely-shredded  cheese  is  placed  in  the  tube  and  decom- 
posed with  20  c.c.  hydrochloric  acid  of  specific  gravity  i.i, 
containing  about  19  per  cent.  HC1.  On  cautiously  warming 
over  wire  gauze,  the  melted  fat  rises  to  the  surface.  After 
cooling,  30  c.c.  of  ether  are  added  and  the  tube  warmed  very 
gently  until  the  acid  and  ethereal  solution  of  fat  separate 
sharply.  Centrifugal  force  helps  this,  but  is  not  essential. 
After  the  volume  of  ether  has  been  read  off,  20  c.c.  are 
pipetted  off  into  a  weighed  Erlenmeyer  flask.  From  this, 
the  quantity  of  fat  in  the  entire  solution  may  be  calculated. 

Lactose. — This  may  be  estimated  by  boiling  the  finely  di- 
vided cheese  with  water,  filtering,  and  determining  the  reduc- 
ing power  of  the  filtrate  on  Fehling's  solution. 

Determination  of  Proteid  Nitrogen  (Stutzer's  Method). — 0.7 
to  0.8  gram  of  the  cheese  are  placed  in  a  beaker,  heated  to 
boiling,  2  or  3  c.c.  of  saturated  alum  solution  added  to  decom- 
pose alkaline  phosphate,  then  copper  hydroxid  mixture  (see 
page  46)  containing  about  0.5  gram  of  the  hydroxid,  and 
stirred  in  thoroughly ;  when  cold,  the  mass  is  filtered,  washed 
with  cold  water,  and,  without  removing  the  precipitate  from 
the  filter,  the  nitrogen  determined  by  the  Kjeldahl-Gunning 
method.  Before  distillation,  sufficient  potassium  sulfid  solu- 
tion must  be  added  to  precipitate  the  copper. 

Ammonium  Compounds. — About  5  grams  of  cheese  are 
rubbed  up  in  a  mortar  with  water,  transferred  to  a  filter,  and 
washed  with  a  liter  of  cold  water.  The  filtrate  is  concentrated 
by  boiling  (if  alkaline,  it  must  be  neutralized  before  heating), 


246  FOOD    ANALYSIS 

barium  carbonate  added,  the  liquid  distilled,  and  the  ammonium 
hydroxid  in  the  distillate  estimated  by  titration  with  standard 
acid. 

According  to  Stutzer,  magnesia  or  magnesium  carbonate 
(the  latter  usually  contains  some  magnesia)  should  not  be 
used  to  free  the  ammonia,  as  some  of  the  amido-compounds 
may  be  decomposed. 

Amido-compounds. — The  nitrogen  as  amido-compounds  is 
estimated  by  subtracting  from  the  figure  for  total  nitrogen 
the  sum  of  the  proteid  and  ammoniacal  nitrogen.  If  nitrates 
are  present,  the  nitrogen  as  such  should  also  be  determined 
and  subtracted. 

Van  Ketel  and  Antusch  propose  the  following  methods  for 
estimating  the  nitrogen  compounds  : 

Ammonium  Compounds. — The  sample,  powdered  with  the 
addition  of  sand,  is  distilled  with  water  and  barium  carbonate, 
and  the  distillate  received  in  a  measured  quantity  of  standard 
sulfuric  acid,  and,  after  boiling,  the  excess  of  acid  is  neutral- 
ized with  standard  sodium  hydroxid,  using  rosolic  acid  as 
indicator. 

Amido-compounds. — These  are  estimated  by  macerating  the 
powdered  cheese  in  water  for  15  hours  at  the  ordinary  tem- 
perature. After  adding  a  little  dilute  sulfuric  acid  (i  14),  the 
proteids  and  peptones  are  precipitated  by  phosphotungstic 
acid.  The  precipitate  is  filtered  off  and  washed  with  water 
containing  a  little  sulfuric  acid.  The  filtrate  is  made  up  to  a 
definite  bulk,  and  the  nitrogen  is  determined  in  an  aliquot  por- 
tion of  the  liquid  by  the  Kjeldahl-Gunning  process,  allow- 
ance being  made  for  the  nitrogen  existing  as  ammonium. 

Peptones  and  Albumoses. — These  are  determined  jointly  by 
boiling  the  powdered  cheese  (mixed  with  sand  as  before)  with 
water  and  filtering  from  the  un dissolved  casein  and  albumin. 
In  an  aliquot  portion  of  the  filtrate  the  peptones  and  albu- 
moses  are  precipitated  by  adding  dilute  sulfuric  acid  and 


CHEESE  247 

phosphotungstic  acid.  After  washing  with  acidulated  water 
the  nitrogen  in  the  precipitate  is  determined  by  the  Kjeldahl- 
Gunning  process. 

The  total  nitrogen  of  the  cheese  is  also  determined,  and 
after  allowing  for  the  nitrogen  existing  as  other  forms,  the 
balance  is  calculated  to  casein. 

Poisonous  Metals, — Lead  chromate  has  been  found  in  the 
rind  of  cheese,  and  finely  divided  lead  in  a  number  of  Cana- 
dian cheeses.  In  England  zinc  sulfate  has  been  employed 
under  the  name  of  cheese  spice  to  prevent  the  heading  and 
cracking.  Arsenic  has  also  been  found  ;  it  may  be  detected 
by  Reinsch's  test.  Lead,  zinc,  and  chromium  may  be 
detected  by  ashing  a  portion  of  the  sample  in  a  porcelain  cru- 
cible and  proceeding  as  on  page  68. 

ANALYSES  OF  VARIOUS  CHEESES 
(Reports  by  W.  A.  Chattaway,  T.  M.  Pearmain,  and  C.  G.  Moor) 

REICHKRT-MEISSL 
NAME.         WATER.      ASH.        FAT.       NUMBER.       N. 

Cheddar, 33.0  4.3  29.5  24.2  4.31 

C-orgonzola,     .    .    .    .40.3  5.3  26.1  22.1  4.36 

Dutch,      41.8  6.3  10.6  27.0  5.11 

Gruyere, 28.2  4.7  28.6  30.0  4.93 

Stilton, 19.4  2.6  42.2  29.0  4.73 

Cheshire, 37.8  4.2  31.3  31.6  4.03 

Gloucester, 33.1  5.0  23.5  31.4  4.99 

Camembert,     ...  47.9  4.7  41.9  31.0  3.83 

Parmesan, 32.5  6.2  17.1  28.0  6.86 

Roquefort,        ....  29.6  6.7  30.3  36.8  4.45 

Double  Cream,    .    .    .  57.6  3.4  39.3  31.2  3.14 

Filled  (United  States),  30.6  3.6  27.7  3.0  4.84 

The  common  American  cheese  is  known  as  Cheddar. 
According  to  L.  L.  Van  Slyke,  this  has,  when  ripe,  about  the 
following  average  composition  : 

Water, 31-5°  Per  cent. 

Fat, 37-OO        " 

Proteids, 26.25         " 

Ash,  sugar,  etc., 5.25         " 


248  FOOD    ANALYSIS 

FERMENTED  MILK  PRODUCTS 

The  usual  fermentation  of  milk  is  the  conversion  of  the 
lactose  into  lactic  acid,  but  by  special  methods  other  changes 
may  be  substituted.  These  modified  fermentations  are  of 
rather  ancient  origin,  and  being  produced  by  mixture  of 
organisms,  the  products  are  complex  and  irregular.  The 
proteids  are  more  or  less  changed  into  proteoses  and  pep- 
tones. 

Kumiss  is  milk  which  has  undergone  alcoholic  fermentation. 
The  inhabitants  of  the  steppes  of  Russia  prepare  it  from 
mare's  milk.  When  cow's  milk  is  used,  cane-sugar  must  be 
added.  It  is  often  made  by  adding  cane-sugar  and  yeast  to 
skim-milk. 

P.  Vieth  gives  the  following  analyses  of  kumiss  at  succes- 
sive stages  of  fermentation  : 

KUMISS  FROM  COW'S  MILK 

ONE  ONE  THREE 

ONE  DAY.       WEEK.       MONTH.      MONTHS. 

Alcohol, I.I  0.9  i.o  I.I 

Solids,      II.3  8.9  86     -        8.5 

Fat,      1.6  1.4  i-5  I-5 

Casein,     ........  2.0  2.0  1.9  1.7 

Albumin, 0.3  0.2  0.2  o.  I 

Sugar, 6.1  3.1  2.2  1.7 

Lactic  acid, 0.2  0.9  1.3  1.9 

Lactoproteid  and  peptone,  0.3  0.5  0.7  0.9 

Soluble  ash, o.i  0.2  0.2  0.2 

Insoluble  ash, 0.4  0.3  0.3  0.3 

The  item  "  lactoproteid  and  peptone"  refers  to  the  sub- 
stances precipitated  by  tannin  after  removal  of  the  casein  and 
albumin. 

KUMISS  FROM  MARE'S  MILK 


AT  THE 

NITROGENOUS 

LACTIC 

END  OF: 

ALCOHOL. 

FAT. 

MATTERS. 

ACID. 

SUGAR. 

ASH. 

I  day,    . 

.  2.47 

1.  08 

2.25 

0.64 

2.21 

0.36 

8  days,  . 

.  2.70 

I-I3 

2.OO 

1.16 

0.69 

0-37 

22      "       . 

.  2.84 

1.27 

I.97 

1.26 

0.51 

0.36 

FERMENTED  MILK  PRODUCTS  249 

Kefyr. — This  is  usually  made  from  cow's  milk.  It  has 
been  used  in  the  Caucasus  for  centuries.  For  its  preparation 
a  peculiar  ferment  is  used,  which  is  contained  in  the  kefyr 
grains.  These  are  first  soaked  in  water,  by  which  they  are 
caused  to  swell,  and  are  rendered  more  active  and  then  added 
to  the  milk.  If  taken  out  of  the  milk  and  dried,  the  grains 
may  be  used  repeatedly. 

The  following  are  analyses  of  kefyr : 

KONIG.  HAMMARSTEN. 

Alcohol, 0.75  0.72 

Fat, 1.44  3-°8 

Casein 2.88  2.94 

Albumin, 0.36  0.18 

Hemialbumose, 0.26  0.07 

Peptone, 0.04 

Sugar, 2.41  2.68 

Lactic  Acid, 1.02  0.73 

Ash, 0.68  0.71 

According  to  Konig,  good  kefyr  will  not  contain  more  than 
i  per  cent,  of  lactic  acid. 

Analytic  Methods. —  Fixed  solids  and  ash  are  determined 
by  evaporations  of  a  weighed  amount  in  a  platinum  basin  as 
described  on  page  36.  Acidity  is  determined  by  filtration 
with  ^  alkali,  using  phenolphthalein  or  methyl-orange  as  an 
indicator.  The  amount  of  acidity  is  expressed  in  terms  of 
lactic  acid.  The  Kjeldahl-Gunning  method  will  give  the  total 
nitrogen.  For  further  examination  of  the  nitrogenous  bodies, 
the  methods  given  on  pages  245  and  246  may  be  applied.  Total 
reducing  sugars  may  be  estimated  as  given  on  page  1 16.  If 
sucrose  and  common  yeast  have  been  added,  the  fermented 
material  will  be  likely  to  contain  invert-sugar,  with  unchanged 
lactose  and  sucrose,  and  the  method  of  examination  of  sweet- 
ened condensed  milk  may  be  applicable.  Fat  can,  probably 
in  all  cases,  be  determined  with  sufficient  accuracy  by  the  L- 
B.  process.  If  it  be  desired  to  make  polarimetric  readings, 
the  liquid  should  be  clarified  with  acid  mercuric  nitrate  solu- 


25O  FOOD    ANALYSIS 

tion  (page  213),  as  some  partly  hydolyzed  proteids  which  have 
rotatory  power  may  not  be  precipitated  by  other  reagents.  The 
determination  of  alcohol  accurately  is  difficult,  as  the  quan- 
tity is  usually  small.  The  cautious  distillation  of  a  consider- 
able volume  of  the  material  previously  neutralized  with  a  little 
sodium  hydroxid  will  yield  a  distillate  in  which  alcohol  may 
be  determined  by  specific  gravity. 

Preservatives  are  not  likely  to  be  used,  since  they  would 
interfere  with  the  fermentation,  but  attempts  may  be  made  to 
secure  better  keeping  by  adding  some  preservative  after  the 
fermentation  has  occurred.  In  some  cases,  therefore,  tests 
for  boric  acid,  formaldehyde,  and  salicylic  acid  should  be  made, 
as  these  will  be  most  likely  to  be  used. 


TEA 


251 


NON-ALCOHOLIC  BEVERAGES 

TEA 

Tea  is  the  prepared  leaf  of  several  species  of  T/iea.  Black 
and  green  tea  are  derived  from  the  same  plant,  the  difference 
being  due  to  the  preparation.  The  quality  of  tea  depends 


FIG.  46. 

a,  Flowery  pekoe  ;  b,  orange  pekoe  ;  c,  pekoe  ;  of,  souchong  1st ;  f,  souchong  >d  ; 
ft  congou;  a  and  b  (mixed),  pekoe;  a,  b,  c,  d,  e  (mixed),  pekoe  souchong. 

much  upon  the  age  of  the  leaf  and  the  time  of  picking. 
Many  pickings  are  made  in  a  season,  the  first  being  of  the 
finer  quality.  The  above  figure,  due  to  Money,28  indicates 
the  leaves  that  constitute  the  different  kinds  of  tea,  classified 
according  to  age. 


252  FOOD    ANALYSIS 

Black  tea  is  prepared  by  exposing  the  leaves  to  the  sun 
until  they  have  withered.  They  are  then  rolled  and  again  set 
aside,  usually  in  the  sun,  covered  with  a  white  cloth  until  fer- 
mentation takes  place.  They  are  then  exposed  in  a  thin 
layer  until  they  have  become  quite  dark,  and  are  finally  dried 
by  heat. 

Green  tea  undergoes  no  fermentation.  In  Japan,  the  leaves 
are  steamed  until  soft,  rolled,  and  dried  ;  in  China,  they  are 
heated  in  pans. 

In  addition  to  tannin  and  the  usual  plant  constituents,  tea 
contains  a  notable  proportion  of  caffein.  In  a  given  variety 
of  tea,  the  proportion  of  caffein  usually,  but  not  always, 
bears  some  relation  to  the  quality,  and  so  does  the  soluble 
ash  and  water-extract. 

Caffein  (thein),  trimethylxanthin,  has  been  found  in  tea, 
coffee,  mate  (Paraguay  tea),  guarana,  and  kola.  When 
slowly  crystallized  from  its  solution  in  chloroform  or  water,  it 
forms  light,  silky,  flexible  needles.  These  are  said  to  con- 
tain one  molecule  of  water,  but  the  proportion  actually  found 
by  experiment  corresponds  to  rather  less,  owing  probably  to 
loss  by^  efflorescence.  On  heating  to  100°  the  alkaloid 
becomes  anhydrous.  If  the  heating  be  long  continued,  a 
little  caffein  is  volatilized,  but  it  does  not  volatilize  with 
steam.  It  melts  at  231-233°,  and  at  384°  boils  with  partial 
decomposition.  It  is  slightly  soluble  in  cold  water,  but  dis- 
solves readily  in  hot,  giving  a  bitter  solution.  It  is  somewhat 
soluble  in  rectified  spirit,  less  so  in  absolute  alcohol,  only  . 
sparingly  in  cold  ether,  nearly  insoluble  in  petroleum  spirit, 
and  freely  soluble  in  chloroform  and  benzene.  It  is  decom- 
posed by  heating  with  dilute  solution  of  sodium  hydroxid, 
barium  hydroxid,  or  calcium  hydroxid. 

The  following  analyses  by  Kozai  indicate  the  difference  in 
composition  between  green  and  black  Japan  teas.  The 
figures  represent  percentage  on  the  dry  material  : 


TEA  253 

ORIGINAL  LEAVES.    GREEN  TEA.    BLACK  TEA. 


Crude  fiber,    
"       protein,  .    . 
Ether  extract,     
Other  nitrogen-free  extract,  .    .    . 
Ash,    

.  10.44 
•  37-33 
•    6-49 
.  27.86 

•    4-97 

10.06 

37-43 
5-52 
31-43 

4.Q2 

10.07 
38.90 
5.82 

35-39 
4.  q-j 

Caffein,   

r^o 

3.  20 

Tannin 

12  QI 

J  . 
10  64. 

o 

Water-extract,    
Nitrogen,  total,      
"        of  albuminoid,  .    .    . 
"        of  caffein,  ...         .    . 
"        of  amido-compounds,  . 

•  50-97 
•    5-97 
.    4.11 
.    0.96 
.    0.91 

53-74 
5-90 
3-94 
0-93 
«.I3 

47-23 
6.22 

4.11 

0.96 
1.16 

The  proportion  of  tannin  found  in  black  tea  is  only  about 
one-half  that  of  the  green  tea. 

Comparing  the  same  varieties  of  tea,  it  will  be  seen  that 
the  commercial  value  is  proportional  to  the  percentage  ol 
soluble  ash,  extract,  tannin,  and  caffein. 

Indian  teas.      Results  from  a  great  number  of  examinations  ; 

Moisture, 5.83  to    6.32  per  cent. 

Insoluble  leaf, 47-12  55.87 

Extract, 37.80  40.35 

Tannin, 13.04  18.87 

Caffein, 1.88  3.24 

Ash,  total, 5.05  6.02 

"     soluble  in  water, 3.12  4.28 

"     insoluble  in  acid, 0.12  0.30 

It  is  probable  that  the  proportion  of  cafifein  in  the  above 
analyses  is  slightly  underestimated.  The  determination  was 
made  by  treating  the  watery  extract  with  magnesia,  evapo- 
rating to  dryness,  and  extracting  with  ether. 

AS  is  evident  from  the  proportion  of  tannin  noted  above, 
Indian  teas  are  much  more  astringent  than  Japan  or  China 
teas. 

The  tea-leaf  is  ovate-lanceolate  with  short  stem  not  sharply 
distinguished  from  the  blade.  The  distal  two-thirds  of  the 
leaf  is  marked  by  serrations  with  slightly  curved  spines.  At 
the  insertion  of  these  spines  the  leaf  tissue  is  thickened.  This 
structure  is  wanting  in  young  leaf  buds  (flowery  pekoe).  The 


254 


FOOD    ANALYSIS 


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TEA  255 

venation  is  a  midrib  running  to  the  extreme  end  of  the  leaf 
with  frequent  lateral  nearly  opposite  branchings  anastomosing 
near  the  edge  and  sending  off  secondary  branches  to  the  ex- 
treme edge.  The  apex  of  the  tea  leaf  is  often  distinctly 
notched,  whereas  most  other  leaves  are  pointed. 

The  stomata  and  hairs  are  fairly  characteristic  ;  the  annexed 
figure  is  from  J.  Moeller's  work. 


Fir:.  47- 
JT/,  Stomata;  A,  hair  ;  m,  cells  containing  chlorophyl.      (X  160.) 

Adulteration. — The  substitution  of  inferior  grades  of  tea 
for  those  of  finer  aroma  and  strength  is  the  common  adulter- 
ation of  tea.  Other  forms  are  :  additions,  such  as  sand,  ex- 
hausted leaves,  foreign  leaves,  and  materials  to  increase  astrin- 
gency,  especially  catechu.  Green  tea  is  often  colored  or 
"  faced  "  with  Prussian  blue,  indigo,  or  turmeric,  and  black 
tea  with  graphite.  Lie  tea  is  an  imitation  made  of  dust  and 
sweepings  of  tea  or  other  leaves  along  with  mineral  matter  of 
various  kinds  and  held  together  by  means  of  starch  or  gum. 
It  is  readily  detected  by  the  addition  of  hot  water,  when  the 
mass  breaks  down  into  the  fragments  of  which  it  is  composed. 


256  FOOD    ANALYSIS 

The  following  analyses  of  spurious  teas,  received  from  the 
United  States  Consuls  at  Canton  and  Nagasaki  (Japan),  were 
made  by  J.  B.  Battershall :  29 


Total  ash,  

i. 
.    8.62 

2. 

8.00 

3- 
7.qc 

4- 

i2.<;8 

Ash  insoluble  in  water,    . 
Ash  soluble  in  water,  .    . 
Ash  insoluble  in  acid, 
Extract,     
Gum,      .    .    .    .    . 

•    7-98 
.    0.64 
•    3-92 
•    7-73 
10.67 

.7 

6.04 

1.86 

3-18 
14.00 
7.  ?o 

/      .7  D 

4-95 
3.00 
1.88 
12.76 

II.OO 

*  *"  j^ 

8.74 
3.84 
6.60 

22.  IO 
1  1  4O 

Insoluble  leaf, 

/ 
7O.6O 

/  o 

70.  « 

67  oo 

.  ^~r 

60.  10 

Tannin,  
Caffein,  

/ 

•    3-13 
.    0.58 

/         J  J 

8.01 
none 

\J  1  .  *-/ 

14-5° 
o.  16 

15.64 

0.12 

1.  Partially  exhausted  and   refired  tea  leaves,   known   as 
"  Ching  Suey  "  (clear  water),  which  name  doubtless  has  refer- 
ence to  the  weakness  of  a  beverage  prepared  from  the  article. 

2.  "  Lie  tea,"  made  from  Wampan  leaves. 

3.  A  mixture  of  10  per  cent,  green  tea  and  90  per  cent, 
"lie  tea,"  sometimes  sold  as  "Imperial"  or  "  Gunpowder" 
tea. 

4.  "  Scented  caper  tea,"  consisting  of  tea  dust  made  up 
into  little  shot-like  pellets  by  means  of  "  Congou  paste  "  (i.  e.t 
boiled  rice). 

ANALYTIC  METHODS. 

Water. — This  is  determined  as  on  page  36.  A  slight 
amount  of  caffein  may  be  lost  in  the  drying  and  counted  as 
water,  but  the  error  so  introduced  is  negligible. 

Ash. — Soluble  ash  and  alkalinity  of  soluble  ash.  (See 
page  48.) 

Extract. — 2  grams  of  the  finely  powdered  tea  are  boiled  for 
an  hour  in  a  flask  provided  with  a  reflux  condenser.  The 
liquid  is  decanted  and  the  residue  boiled  for  a  short  time 
with  successive  portions  of  50  c.c.  of  water  until  this  is  no 
longer  colored.  The  solutions  are  mixed,  heated,  filtered 
through  a  tared  filter,  to  which  the  insoluble  leaf  is  also 
transferred.  After  washing  with  boiling  water,  the  filter  and 


TEA  257 

contents  are  dried  to  constant  weight.  The  extract  is  deter- 
mined by  difference,  or,  if  desired,  the  filtrate  is  made  up  to  a 
definite  volume,  and  an  aliquot  portion  evaporated  and  dried 
at  1 00°  and  weighed. 

Nitrogen. — The  total  nitrogen  is  determined  by  the  method 
described  on  page  41.  Albuminoid  nitrogen  is  determined 
by  Stutzer's  method  (page  46). 

Caffcin. — This  is  best  determined  by  A.  H.  Allen's  method  : 
6  grams  of  the  finely  powdered  tea  and  600  c.c.  of  water  are 
boiled  under  a  reflux  condenser  for  six  or  eight  hours  ;  4 
grams  of  lead  acetate  in  powder  are  then  added  and  the  liquid 
again  boiled  for  ten  minutes.  If,  on  removing  the  source  of 
heat,  the  precipitate  does  not  curdle  and  settle  readily,  leaving 
the  liquor  colorless  or  nearly  so,  a  further  addition  of  lead 
acetate  must  be  made  and  the  boiling  repeated.  When 
clarification  is  effected,  the  liquid  is  passed  through  a  dry 
filter,  500  c.c.  of  the  filtrate  (5  grams  of  the  tea)  are  evapo- 
rated to  about  50  c.c.,  and  a  little  disodium  hydrogen  phos- 
phate is  added  to  precipitate  the  remaining  lead.  The  liquid 
is  filtered,  the  precipitate  washed,  and  the  filtrate  further  con- 
centrated to  about  40  c.c.,  when  the  cafTein  is  extracted  by 
at  least  four  agitations  with  -chloroform.  The  separated 
chloroform  solutions  are  mixed,  and  distilled  in  a  tared  flask 
immersed  in  boiling  water.  While  the  flask  is  still  hot  the 
last  traces  of  chloroform  are  removed  by  a  current  of  air,  and 
the  residual  alkaloid  is  weighed. 

Determinations  of  caffein  based  upon  the  treatment  of  the 
leaves  with  boiling  lime  water  or  other  alkali  are  valueless,  as 
the  alkaloid  is  decomposed  by  such  treatment.  The  process 
of  Paul  and  Cownley,  by  which  the  leaves  are  treated  with 
magnesia  and  the  dried  mixture  exhausted  by  alcohol,  has 
been  shown  to  furnish  results  below  the  truth. 

The  following  volumetric  method,  due  to  H.  Gomberg,  has 
been  reported  upon  favorably  by  E.  F.  Ladd : 


258  FOOD    ANALYSIS 

A  weighed  quantity  of  the  tea  is  boiled  with  water  as  above, 
the  solution  made  up  to  a  known  volume,  and  filtered.  An 
aliquot  portion  of  the  filtrate  is  treated  with  lead  subacetate 
so  long  as  a  precipitate  is  formed.  After  standing,  the  pre- 
cipitate is  filtered  off,  the  excess  of  lead  carefully  removed  by 
hydrogen  sulfid,  the  filtrate  from  the  lead  sulfid  boiled  to 
remove  hydrogen  sulfid,  and  divided  into  two  equal  parts. 
One  portion  is  acidified  with  sulfuric  or  hydrochloric  acid  and 
excess  of  decinormal  iodin  solution  added  ;  after  standing  5 
to  10  minutes  it  is  filtered  and  the  filtrate  titrated  with  deci- 
normal thiosulfate  solution.  If,  in  the  other  portion,  potas- 
sium iodid-iodin  solution  (page  35)  produces  a  precipitate,  a 
correction  is  necessary,  i  c.c.  of  decinormal  thiosulfate  cor- 
responds to  0.00485  gram  of  caffein. 

Facing. — The  coloring-matter  used  in  facing  is  usually 
present  in  minute  amount,  and  is  best  detected  by  the  micro- 
scope, the  leaf  being  examined  by  reflected  light.  A  good  plan 
is  to  shake  some  of  the  leaves  with  water,  allow  the  suspended 
matter  to  settle,  and  examine  the  sediment  by  the  microscope 
and  chemically.  Prussian  blue  may  be  distinguished  from 
indigo  by  the  fact  that  the  color,  of  the  former  is  discharged 
by  addition  of  sodium  hydroxid.  Indigo  forms  a  deep  blue 
solution  with  sulfuric  acid.  Turmeric  is  detected  as  noted 
under  "  Mace."  Graphite  may  be  detected  by  examination 
under  the  microscope. 

Added  Mineral  Matter. — Any  considerable  addition  of 
mineral  matter  will  be  shown  by  the  increased  proportion  of 
ash,  which  usually  ranges  from  5  to  6.5  per  cent.,  and  only 
in  exceptional  cases  rises  to  7.5  per  cent.  Magnetic  iron 
oxid  and  particles  of  iron  have  been  found  in  tea,  and  may  be 
readily  separated  from  it  by  the  magnet.  Sand  and  powdered 
brick  have  also  been  found.  The  former  may  be  accidental. 

Exhausted  Tea  Leaves. — The  detection  of  admixture  of 
moderate  proportion  of  added  tea  leaves  is  difficult.  Con- 


TEA  259 

siderable  addition  will  be  indicated  by  the  decreased  propor- 
tion of  extract  and  caffein,  and  especially  of  soluble  ash  and 
its  alkalinity.  The  soluble  ash  of  pure  tea  is  from  2.5  to  4 
per  cent.,  and  is  usually  over  3  per  cent,  whereas  that  ot 
exhausted  tea  is  generally  not  over  0.8  per  cent.  The  alka- 
linity of  the  soluble  ash  expressed  as  potassium  oxid  is  from 
1.25  to  2  per  cent,  (calculated  on  the  dry  tea).  In  exhausted 
tea  the  alkalinity  is  likely  to  be  less  than  0.3  per  cent. 

The  soluble  ash  is  best  calculated  to  percentage  of  total  ash. 
The  interference  of  sand  may  be  eliminated  by  calculating  the 
proportion  of  ash  soluble  in  water  to  that  soluble  in  acid. 
Wigner  obtained  the  following  average  results  from  the  ex- 
amination of  67  samples  of  tea  : 

Siliceous  matter, 7.96  per  cent. 

Soluble  in  acid, 37-54       " 

"       ««  water,      54-5°       " 

Alkalinity  of  soluble  ash,  25.09  per  cent. 

Excluding  the  portion  insoluble  in  acid,  the  figures  become  : 

Soluble  in  water, 59.21  per  cent. 

Alkalinity  of  soluble  ash, 27.26       " 

A  proportion  of  soluble  ash  to  total  ash  less  than  40  per 
cent.  (45  per  cent.,  excluding  siliceous  matter)  gives  rise  to 
suspicion  of  adulteration  with  exhausted  leaves. 

The  minimum  proportion  of  extract  yielded  by  pure  tea  is, 
according  to  the  standard  fixed  by  the  Society  of  Public 
Analysts  in  1874,  not  less  than  30  per  cent.  ,  The  proportion 
usually  found  much  exceeds  this  figure,  but  congou  may 
contain  less.  The  proportion  of  caffein  found  by  different 
observers  ranges  from  1.8  to  4  per  cent,  the  lower  propor- 
tions being  found  in  Japan  teas. 

Exhausted  leaves  have  in  some  instances  been  found  to  be 
partly  unrolled  or  much  frayed  and  broken,  and  more  posi- 


260  FOOD    ANALYSIS 

tive  indications  might  be  had  by  the  examination  of  selected 
leaves  of  suspicious  appearance. 

Foreign  Astringents. — Catechu  is  sometimes  added,  especi- 
ally to  "  lie  "  or  "  caper  "  tea,  or  to  mask  the  presence  of 
exhausted  leaves.  It  may  be  detected  by  Hager's  test  : 
About  a  gram  of  the  sample  is  boiled  with  water,  the  extract 
treated  with  excess  of  lead  monoxid,  and  filtered.  A  solu- 
tion of  silver  nitrate  is  added  to  clear  the  filtrate  ;  in  the 
presence  of  catechu,  a  yellow  flocculent  precipitate,  which  rap- 
idly becomes  dark,  is  formed.  Pure  tea  gives  only  a  slight 
grayish  precipitate  of  silver.  A.  H.  Allen  recommends  the 
following  process,  which  should  be  applied  to  the  suspected 
tea,  side  by  side  with  a  genuine  sample  :  I  gram  of  the  pure 
tea,  and  an  equal  weight  of  the  suspected  sample,  are  infused 
in  separate  portions  of  100  c.c.  each  of  boiling  water,  and  the 
strained  liquid  precipitated  while  boiling  with  a  slight  excess 
of  neutral  lead  acetate.  20  c.c.  of  the  filtrate  from  the  pure 
tea  (which  should  be  colorless),  when  cautiously  heated  and 
treated  with  a  few  drops  of  silver  nitrate  solution,  avoiding 
excess,  gives  only  a  very  slight  grayish  cloud  or  precipitate 
of  reduced  silver  ;  but  the  same  tea  containing  2  per  cent,  of 
added  catechu  gives  a  copious  brownish  precipitate,  the  liquid 
acquiring  a  distinctly  yellowish  tinge.  With  a  somewhat 
larger  proportion  of  catechu,  the  filtrate  from  the  lead  precipi- 
tate gives  a  bright  green  color  on  adding  one  drop  of  dilute 
ferric  chlorid,  while  the  solution  from  pure  tea  gives  only  a 
slight  reddish  color,  due  to  the  presence  of  acetate.  On 
allowing  the  liquid  to  stand,  the  adulterated  tea  gives  a  pre- 
cipitate of  a  grayish  or  olive-green  color,  the  pure  tea  under- 
going no  change. 

Foreign  Leaves. — A  small  proportion  of  foreign  leaves, 
such  as  those  of  the  rose,  jasmine,  and  orange,  are  sometimes 
added  to  impart  bouquet,  but  these  are  usually  removed  be- 
fore packing.  Other  foreign  leaves,  especially  the  sloe,  wil- 


TEA  26l 

low,  elder,  Chloranthus  inconspicuus,  Camellia  sasanqua,  and 
Eurya  chinensis,  have  been  added  in  considerable  quantity,  but 
the  practice,  so  far  as  concerns  the  tea  shipped  to  the  United 
States,  seems  to  be  less  common  than  formerly.  The  detec- 
tion of  such  additions  is  best  made  by  the  appearance  of  the 
leaf  and  the  microscopic  examination,  but  a  few  chemical  tests 
have  been  proposed  which  may  be  of  some  assistance.  A. 
W.  Blyth  proposes  to  utilize  the  presence  of  manganese, 
which  is  a  constant  constituent  of  the  ash  of  tea.  The  sus- 
pected leaf  is  ashed  and  the  ash  treated  on  fused  platinum  foil 
with  potassium  nitrate  and  carbonate.  The  distinct  green 
color  due  to  a  manganate  is  readily  recognized.  Allen  has 
applied  the  test  to  various  leaves  and  found  manganese  to  be 
present  in  the  following :  Species  of  Thea  (tea),  Camellia  sa- 
sanqua,  C.  japonica,  coffee,  beech,  blackberry,  and  sycamore. 
Manganese  was  absent  from  the  leaves  of  the  hawthorn,  ash, 
raspberry,  cherry,  plum,  and  rose,  and  only  faint  traces  were 
detected  in  the  leaves  of  the  Ilex  paraguayensis,  elm,  birch, 
lime,  sloe,  elder,  willow  herb,  and  willow.  Blyth  has  also 
proposed  the  following  test,  depending  upon  the  isolation  of  caf- 
fein  and  recognition  by  its  crystalline  form  under  the  micro- 
scope :  The  leaf  or  fragment  is  boiled  for  a  minute  in  a  watch- 
glass  with  a  very  little  water,  an  equal  bulk  of  calcined  mag- 
nesia is  added,  and  the  whole  heated  to  boiling  and  rapidly 
evaporated  to  a  large-sized  drop.  This  drop  is  transferred  to 
a  subliming  cell,  and  if,  after  heating  to  about  1 10°,  no  crys- 
talline sublimate  of  caffein  is  obtained,  the  leaf  cannot  be  a 
tea  leaf.  If,  however,  a  sublimate  of  caffein  is  obtained,  it  is 
not  conclusive  evidence,  since  other  plants  contain  the  alka- 
loid. 

More  satisfactory  results  are  obtained  by  the  examination 
of  the  shape  and  venation  of  the  leaf.  The  sample  should  be 
softened  by  soaking  in  hot  water,  carefully  unrolled,  trans- 
ferred to  a  microscope  slide,  and  examined  with  a  hand  lens. 


262  FOOD    ANALYSIS 

Such  examination  will  usually  be  sufficient,  but  in  doubtful 
cases  it  may  be  necessary  to  use  higher  powers.  (See  plates 
in  Appendix.) 

COFFEE 

COFFEE  is  the  seed  of  species  of  Coffea,  especially  C.  ara- 
bica  L.,  cultivated  in  tropical  countries.  The  fruit  usually 
consists  of  two  seeds  surrounded  by  a  pulp,  which  is  removed 
by  fermenting  and  washing.  The  membranous  pericarp  re- 
moved by  machinery  is  sometimes  roasted  and  used  as  a  sub- 
stitute for  coffee. 

The  following  are  the  more  important  constituents  of  raw 
coffee  :  An  essential  oil,  fat,  caffetannates,  caffein,  and  caf- 
fearin.  The  essential  oil  has  been  little  studied.  The  fat  of 
coffee  is  soluble  in  alcohol,  but  its  composition  is  not  yet 
clearly  ascertained. 

Caffetannic  acid  may  be  obtained  by  diluting  the  alcoholic 
infusion  of  coffee  with  water,  filtering  from  the  precipitated 
fatty  matter,  and  adding  lead  acetate  to  the  boiling  filtrate. 
On  decomposing  the  washed  filtrate  with  hydrogen  sulfid  the 
acid  is  obtained.  It  is  crystalline,  astringent,  soluble  in 
water,  less  soluble  in  alcohol,  and  very  sparingly  in  ether. 
It  gives  a  dark  green  coloration  with  ferric  chlorid,  and  does 
not  precipitate  gelatin. 

Coffee  contains  a  fairly  constant  proportion  of  caffein  (see 
next  page).  According  to  Paladino,  there  is  also  present  a 
narcotic  alkaloid,  which  he  calls  caffearin.  Paladino's  results 
seem  to  be  corroborated  by  those  of  Forster  and  Riechel- 
mann,  who  found  an  alkaloid  distinguished  from  caffein  by 
the  following  characteristics  :  failure  to  respond  to  the  mu- 
rexid  test,  precipitability  by  picric  acid,  and  insolubility  in 
chloroform. 

Roasted  coffee  contains  a  small  amount  of  sugar,  which, 
according  to  Spencer,  consists  largely  of  sucrose.  It  appears 


COFFEE  263 

to  be  absent  from  raw  coffee  and  is  derived  from  the  decom- 
position of  the  glucosids  (tannins). 

The  aroma  of  roasted  coffee  is  due  to  caffeol,  which  may  be 
separated  by  distilling  with  water,  agitating  the  distillate  with 
ether,  and  evaporating.  It  is  an  oily  liquid,  slightly  soluble 
in  hot  water,  but  easily  soluble  in  alcohol  and  ether.  By  fu- 
sion with  caustic  soda  it  yields  sodium  salicylate.  The  phy- 
siological effects  of  coffee  are  attributed  to  the  caffeol,  caffein, 
and  caffearin. 

The  roasting  of  coffee  results  in  a  notable  reduction  of 
some  of  the  constituents,  especially  the  caffein,  fat,  and  sugar. 
When  properly  conducted,  the  total  loss  in  weight  amounts 
to  from  12  to  1 8  per  cent.,  of  which  about  8  per  cent,  repre- 
sents moisture.  Konig  gives  the  following  figures,  calculated 
as  percentage  of  moisture-free  material : 

RAW.  ROASTED. 

Soluble  in  water, 3°-93  28.36 

Total  nitrogen, 2.21  2.38 

Caffein, 1.33  1.42 

Fat, 14.91  16.14 

Sugar, 3.66  1.35 

Fiber, 31.24  25.07 

Other  nitrogen-free  matter, 34-55  39-84 

Ash, 3.92  3.87 

Coffee  is  sometimes  glazed  with  sugar  before  roasting. 
According  to  Konig,  when  so  treated  it  retains  much  more 
moisture.  According  to  Hilger  and  Juckenack,  glazed  coffee 
requires  to  be  heated  to  a  much  higher  temperature,  which 
results  in  about  double  the  usual  loss  of  caffein  and  fat. 

ADULTERATION. — Raw  coffee  is  subject  to  less  adulteration 
than  roasted  and  especially  ground  coffee.  Coffee  beans  differ 
considerably  in  size  and  quality  according  to  their  origin,  and 
the  inferior  kinds  are  sometimes  so  treated  as  to  give  them  the 
appearance  of  the  better  qualities.30 

West  India  coffee  is  for  the  most  part  even -sized,  pale  and 


264  FOOD    ANALYSIS 

yellowish,  firm  and  heavy,  with  fine  aroma,  losing  little 
weight  by  the  roasting  process. 

Brazil  coffee  is  larger,  less  solid,  greenish  or  white,  usually 
styled  by  the  brokers  "  low  "  or  "  low  middlings." 

Java  coffee  is  smaller,  slightly  elongated,  pale  in  color, 
light  and  deficient  in  essential  oil. 

Ceylon  coffee  is  of  all  descriptions,  but  the  ordinary  planta- 
tion products  are  even-colored,  slightly  canoe-shaped,  strong 
in  aroma  and  flavor,  heavy,  and  permit  of  adulteration  more 
than  other  kinds. 

Mocha  coffee  is  usually  considered  the  best,  but  very  little 
reaches  the  United  States.  Porto  Rico  coffee  often  is  called 
Mocha.  The  grains  of  Mocha  coffee  are  small  and  dark 
yellow. 

Java  coffee,  when  new,  is  pale  yellow,  and  is  then  cheaper 
than  when  old  and  brown.  This  color  is  partly  the  effect  of 
curing  as  well  as  the  result  of  age. 

The  variation  in  the  size  of  coffee  beans  is  shown  in  the 
following  table,  due  to  Thorpe  : 

NUMBF.R  OF  SEEDS  CONTAINED 
IN  A  50  c.c.  MEASUKE. 

Fine  brown  Java, 187 

Fine  Mysore, 198 

Fine  Neilgherry, 203 

Costa  Rica, 203 

Good  ordinary  Guatemala, 207 

Good  Laguayra,       210 

Good  average  Santos, 213 

Fine  long-berry  Mocha,  .        ....        217 

Good  ordinary  Java, 223 

Fine  Ceylon  plantation, ....  225 

Good  average  Rio, 236 

Medium  plantation  (Ceylon), 238 

Manila, 248 

Ordinary  Mocha, 270 

West  African, 313 

Java  coffee,  being  of  high  price,  has  been  imitated  by  color- 
ing the  cheaper  grades  with  dyes  or  mineral  pigments. 

According  to  Waller,  Java  coffee  is  imitated  by  exposing 


COFFEE  265 

South  American  coffee  to   a   high  moist  heat,  by  which  the 
color  is  changed  from  green  to  brown. 

Raw  coffee  is  heavier  than  water.  Fade  gives  the  specific 
gravity  of  raw  coffee  berries  at  from  1.041  to  1.368.  Dam- 
aged coffee  that  has  been  washed  and  partially  roasted  to 
improve  the  color  may  have  a  specific  gravity  less  than  i. 
Roasted  coffee  has  a  specific  gravity  of  from  0.500  to  0.635, 
but  samples  that  have  been  made  to  take  up  much  water  by 
steaming  and  then  coating  with  glycerol  or  sugar  (see  page 
263)  may  possess  a  specific  gravity  appreciably  higher  (0.650 
to  0.770).  Implicit  reliance  should  not  be  placed  upon  these 
figures,  since  over-roasted  coffees  may  be  heavier  than  water. 
The  specific  gravity  of  raw  coffee  may  be  determined  by  im- 
mersing the  beans  in  strong  brine  and  cautiously  adding 
water  until  they  remain  suspended  in  the  liquid.  The  specific 
gravity  of  the  liquid  is  then  determined  as  usual.  In  the 
case  of  roasted  coffee  the  brine  is  replaced  by  petroleum  spirit 
to  which  is  gradually  added  ordinary  petroleum. 

Adulteration  with  exhausted  coffee  beans  is  reported  by 
Roos.  The  samples  examined  yielded  only  I  per  cent,  of 
ether  extract. 

Facing. — The  following  are  reported  to  have  been  used  as 
"facing"  for  coffee.  Scheele's  green,  chrome  yellow,  ochre, 
silesian  blue,  burnt  umber,  Venetian  red,  charcoal,  indigo, 
ultramarine  blue,  clay,  gypsum.  A  blue  color  is  also  said  to 
be  produced  by  shaking  the  beans  with  finely  powdered  iron. 
The  beans  are  sometimes  polished  by  rotating  in  a  cylinder 
with  soapstone. 

The  examination  for  facing  should  be  made  with  the  micro- 
scope, and  also  by  shaking  with  water  and  examining  the 
sediment,  as  described  under  tea  (page  258).  Artificial  colors 
may  usually  be  detected  by  treating  the  beans  with  strong 
alcohol,  evaporating  to  dryness,  and  testing  the  residue  (see 
pages  77  and  79). 
23 


266  FOOD    ANALYSIS 

Imitation  beans  have  frequently  been  sold  for  use  in  mixing 
with  coffee.  In  some  cases  these  are  molded  in  close  imita- 
tion of  the  true  beans.  The  material  used  for  the  purpose  is 
sometimes  clay,  but  more  frequently  one  or  more  of  the  fol- 
lowing :  Wheat  flour,  chicory,  bran,  rye,  peas,  and  acorns. 
These  are  often  mixed  with  molasses.  Ferrous  sulfate  has 
also  been  found. 

Most  imitation  coffee  is  heavier  than  water,  but  the  readiest 
means  of  detection  is  by  means  of  the  microscope,  the  appli- 
cation of  the  iodin  test  for  starch,  and  determination  of  the  ash. 

Many  substances  have  been  used  as  substitutes  for  coffee  as 
well  as  for  its  adulteration  ;  among  these  are  chicory,  Mogdad 
and  Mussaenda  coffee,  roasted  cereals  and  leguminous  seeds, 
cocoa  husks,  and  figs. 

Coffee  contains  no  starch,  a  constituent  of  many  adulter- 
ants, such  as  cereals  and  acorns.  It  may  be  detected  by 
Allen's  method  :  The  coffee  is  boiled  for  a  few  minutes  with 
about  ten  parts  of  water.  When  the  liquid  has  become  per- 
fectly cold,  some  dilute  sulfuric  acid  is  added,  a  strong  solution 
of  potassium  permanganate  is  dropped  in  cautiously,  with 
agitation,  until  the  coloring-matter  is  nearly  destroyed,  when 
the  liquid  is  strained  or  decanted  from  the  insoluble  matter 
and  iodin  added.  A  distinct  reaction  occurs  in  the  presence 
of  even  I  per  cent,  of  starch.  In  identifying  the  starch 
granules  with  the  microscope  it  is  advisable  to  make  a  pre- 
liminary extraction  of  the  sample  with  ether,  and  subsequently 
with  alcohol. 

Chicory  is  the  root  of  the  Cichorium  intybus  L.  It  is  distin- 
guished from  coffee  by  the  microscope.  The  cells  of  the 
parenchyma  are  large,  smooth-walled,  and  regular.  The 
milk  ducts  are  branched  and  filled  with  a  coarsely  granular 
material.  The  body  of  the  root  contains  long,  pointed  cells 
presenting  a  characteristic  dotted  appearance.  (See  Fig.  48.) 
Dandelion  and  other  sweet  roots  present  a  somewhat  similar 


COFFEE 


m 


-qu 


structure,  but  the  ducts  are  scaliform,  the  cells  larger,  and 
milk  vessels  are  absent.  It  contains  no  starch.  Rimmington 
recommends  the  following  method  for  the  detection  of 
chicory  :  The  sample  is  boiled  for  a  short  time  with  water 
containing  a  little  sodium  carbonate  ;  the  solution  is  decanted 
and  the  residue  treated  with  a  solution  of  bleaching  powder 
for  several  hours,  when  decolorization  will  be  effected.  The 
coffee  will  be  found  as  a 
dark  stratum  at  the  bottom 
of  the  beaker  and  the  chic- 
ory as  a  light  stratum 
above  it. 

The  following  prelimin- 
ary tests  may  be  of  value 
in  the  detection  of  adultera- 
tion. A  small  quantity  of 
the  ground  material  is 
sprinkled  on  cold  water. 
Coffee  will  usually  float, 
and  impart  very  little  color 
to  the  water.  Chicory  and 
most  other  additions  sink, 
and  the  caramel  contained 
in  them  dissolves  quickly, 
forming  a  dark  and  usually 
turbid  solution.  Coffee 
grains  are  hard,  whereas 

chicory  and  some  other  adulterants,  after  maceration  for 
some  hours  in  water,  are  quite  soft.  At  the  end  of  this  time, 
if  the  mixture  be  transferred  to  a  piece  of  stretched  cloth  and 
rubbed  with  a  pestle,  the  chicory  will  pass  through. 

The  proportion  of  the  adulterant  which  has  been  detected 
by  the  microscope  or  the  preliminary  tests  just  mentioned  may 
often  be  determined  with  a  fair  degree  of  accuracy  by  chemi- 


FIG.  48. 

g,  Vascular  tissue ;  hp,  parenchyma ;  /, 
fibers;  m,  medullary  rays. 


268  FOOD    ANALYSIS 

cal  examination,  especially  by  the  determinations  of  fat, 
caffein,  water  extract,  and  ash. 

The  actual  amount  of  coffee  present  may  be  determined 
by  calculation  from  the  caffein  present.  Paul  and  Cownley 
have  shown  that  most  of  the  published  methods  for  determin- 
ing caffein  give  results  below  the  truth.  They  have  proposed 
the  following  method,  and  recommend  that  it  be  carried  out 
on  the  material  dried  at  100°  in  order  to  eliminate  the  error 
due  to  variable  proportions  of  moisture  and  at  the  same  time 
allow  better  grinding  of  the  sample  and  better  extraction  : 
5  grams  of  the  finely  powdered  dry  material  are  mixed  in  a 
mortar  with  2  grams  of  ignited  magnesia,  the  mixture  thor- 
oughly moistened  with  hot  water,  again  triturated,  dried  at 
1 00°,  extracted  with  boiling  alcohol,  and  the  resultant  liquid 
evaporated  nearly  to  dryness,  boiled  with  50  c.c.  of  water, 
and  treated  with  a  few  drops  of  dilute  sulfuric  acid.  When 
cold,  the  liquid  is  filtered  and  repeatedly  shaken  with  chloro- 
form until  exhausted.  The  chloroform  solution  is  then 
agitated  with  a  very  dilute  solution  of  sodium  hydroxid, 
which  removes  a  little  coloring-matter.  The  chloroform  is 
distilled  off  in  a  weighed  flask  and  the  residue  weighed.  The 
caffein  so  obtained  may  contain  a  small  quantity  of  waxy  or 
resinous  matter  and  may  be  purified  by  solution  in  boiling 
water,  filtration,  and  evaporation  of  the  filtrate. 

The  greatest  care  should  be  taken  that  the  treatment  with 
alcohol  and  chloroform  be  continued  until  no  more  material 
is  extracted.  The  complete  extraction  by  alcohol  is-  es- 
pecially difficult,  and  for  this  reason  it  may  be  preferable  to 
make  the  determinations  as  described  under  tea  (page  257), 
employing  10  or  12  grams  of  the  material.  In  the  presence 
of  chicory  the  extracted  alkaloid  is  liable  to  be  strongly 
colored,  and  Allen  recommends  that  it  be  redissolved  in  water, 
a  few  drops  of  sodium  hydroxid  added,  and  the  liquid  again 
extracted  with  chloroform. 


COFFEE  269 

The  proportion  of  caffein  in  various  coffees,  as  determined 
by  Paul  and  Cownley,  was  found  to  be  fairly  constant,  the 
limits  being  usually  from  1.2  to  1.29  per  cent.,  or,  in  the  case 
of  Liberian  coffee,  1.39  per  cent.  A  proportion  of  1.2  per 
cent,  might  be  taken  as  a  basis  of  calculation. 

Fat. — The  fat  of  coffee  may  be  determined  by  extracting 
with  petroleum  spirit  the  material  dried  at  100°.  According 
to  Macfarlane,  the  petroleum  spirit  extract  from  previously 
dried  coffee  usually  ranges  from  10  to  12  per  cent.  Only  one 
sample  out  of  nearly  fifty  showed  less  than  10,  and  12.5  per 
cent,  was  reached  only  in  a  few  cases. * 

Water-extract. — Valuable  indications  are  often  furnished  by 
the  determination  of  the  amount  of  water-extract,  which  is 
fairly  uniform  and  little  affected  by  the  usual  variations  in 
extent  of  roasting.  The  determination  is  simplified  by  the  ob- 
servation of  the  specific  gravity  of  the  watery  solution,  as  rec- 
ommended by  Graham,  Stenhouse,  and  Campbell. 3 1  One  part 
of  the  sample  is  treated  with  ten  parts  of  water,  the  liquid 
heated  to  boiling,  cooled  to  15.5°,  and  the  specific  gravity 
taken.  The  following  figures  were  obtained  in  this  manner  : 

Mocha  coffee,  .  .  1008.0  Turnips, 1021.4 

Neilgherry  coffee,  .  1008.4  Dandelion, 1021.9 

Plantation  Ceylon  Red  beet,  1022.1 

coffee,  ....  1008.7  Marigold  wurzel, 1023.5 

Native  Ceylon  cof-  Lupins, 1005.7 

fee, 1009.0  Peas, 1007.3 

Java  coffee,  .  .  .  1008.7  Beans, 1008.4 

Jamaica  coffee,  .  .  1008. 8  Brown  malt,  . 1010.9 

Costa  Rica  coffee  .  1009.0  Black  "  1021.2 

"  average,  1008.7  Rye  meal, 1021.6 

Chicory,  .  .  .  1019.1  to  1023.6  Maize, 1025.3 

"  average,  .  IO2I.O  Bread  raspings,  ...  .  .  1026.3 

Parsnips, 1014.3  Acorns, 1007.3 

Carrots, 1017.1  Spent  tan, 1002.1 

According  to  McGill,  the  specific  gravity  of  the  infusions  ot 
coffee  and  chicory  are  materially  affected  by  the  fineness  of 
powder  and  the  time  occupied  in  heating  the  solution  to  boiling, 
and  the  duration  of  the  boiling.  The  following  process  is 


27O  FOOD     ANALYSIS 

recommended  :  10  grams  of  the  dried,  finely  powdered  sample 
are  heated  with  100  c.c.  of  distilled  water  in  a  flask  provided 
with  a  reflux  condenser.  The  heat  is  adjusted  so  that  ebulli- 
tion commences  in  10  to  15  minutes,  and  the  boiling  continued 
for  exactly  one  hour  ;  the  liquid  is  allowed  to  stand  for  1  5 
minutes,  and  then  passed  through  a  dry  filter.  The  average 
specific  gravity  of  the  decoction  from  pure  coffee  was  found  to 
be  1009.86  at  17°,  and  that  of  chicory,  1028.21.  Theamount 
of  coffee  present  in  a  mixture  of  coffee  and  chicory  might  be 
approximately  calculated  from  the  following  formula,  in  which 
C  is  the  percentage  of  coffee  and  d  the  observed  specific 
gravity  at  17°  : 

1028.21  —  d 


0.1835 

J.  Macfarlane  has  determined  the  water-extract  by  boiling 
with  water  the  dried  residue  from  the  determination  of  fat 
(page  269)  and  redrying  and  weighing  the  residue.  The 
water-extract  is  determined  by  difference.  The  following 
results  were  obtained  : 

Coffee  (Santos,  Mocha,  and  Java),    .    .    .  20.4-22.4  per  cent. 
Chicory,     ..............  77.7  "       " 

Hehner  has  found  highly  roasted  chicory  to  give  a  water- 
extract  as  low  as  54.1  per  cent,  and  a  specific  gravity  of  the 
lOper  cent,  solution  of  1019. 

Cassal  has  found  genuine  coffee  to  give  a  water-extract  as 
high  as  29  per  cent.  More  recently  several  observers-  have 
called  attention  to  the  fact  that  the  proportion  of  water-soluble 
matter  in  commercial  chicory  may  be  markedly  greater*  than 
that  found  in  the  above  samples,  examined  years  ago.  This 
appears  to  be  due,  as  pointed  out  by  B.  Dyer,  to  the  less 
roasting  to  which  it  is  subjected.  The  following  results,  due 
to  Dyer,  were  obtained  by  boiling  the  sample  with  water, 
washing,  drying,  and  weighing  the  insoluble  residue,  and 


COFFEE  271 

determining  the  soluble  matters  by  difference.  The  moisture 
varied  in  extreme  cases  from  I  to  4  per  cent.,  but  the  results 
were  calculated  as  percentage  of  the  dried  material  : 

INSOLUBLE  ASH 

IN         ETHER-      NITRO-    TOTAL  SOLUBLE  IN 
WATER.    EXTRACT.      GEN.         ASH.       WATER.      SAND. 

Chicory   "nibs"    described 

as  "  medium  roast,"  .  .  22.40  2.57  1.53  4.63  2.50  0.70 
Chicory  "nibs"  described 

as  "  dark  roast,"  .  .  .  .  $0.30  2.43  1.67  4.70  2.99  0.30 

Ground  chicory,  9  samples,  21.50  1.90  1.23  5.33  1.60  0.77 

to  37.80  to  3.87  to  1.52^  to  8.23  to  3.30  to  3.97 

In  eight  out  of  the  eleven  samples  the  matter  insoluble  in 
water  ranged  from  21.50  to  23.50  per  cent.  One  sample 
contained  35.50,  one  37.80,  and  one  50.30  per  cent. 

Graham,  Stenhouse,  and  Campbell  have  suggested  the  tinc- 
torial power  of  the  infusion  as  a  means  of  determining  adul- 
terants in  coffee.  As  a  rule,  the  coloring  power  of  chicory  is 
about  three  times  as  great  as  that  of  coffee.  The  method 
may  be  useful  in  the  detection  of  added  caramel  or  of  added 
sugar  which  has  been  caramelized  in  roasting.  The  infusion 
should  be  compared  with  that  made  from  pure  coffee. 

The  ash  of  coffee  is  usually  3.5  to  4.5  per  cent,  and 
rarely,  if  ever,  5  per  cent.  Of  this,  about  80  per  cent,  is 
soluble  in  water.  It  contains  no  silica,  or,  at  most,  mere 
traces,  and  is  almost  invariably  white.  A  red  ash  usually 
indicates  adulteration.  A  notable  amount  of  potassium  is 
present,  but  sodium  may  be  present  in  small  amount.  Analy- 
ses by  Ludwig  indicate  that  the  composition  of  coffee  ash  is 
subject  to  marked  variation  according  to  soil.  Chicory  con- 
tains about  6  per  cent,  of  ash,  of  which  only  from  30  to  40 
per  cent,  is  soluble  in  water.  It  may  contain  several  per  cent, 
of  silica  and  usually  carries  considerable  admixed  sand.  So- 
dium is  always  present,  often  to  a  considerable  extent. 

The  ash  of  cereals  and  leguminous  seeds  is  usually  less 
than  that  of  coffee  (see  page  99). 


2/2  FOOD    ANALYSIS 

The  following  table,  due  to  Konig,  gives  some  results 
obtained  from  the  examination  of  various  coffee  adulterants  : 

WATER- 
EXTRACT 
CALCU- 
LATED 

NITRO-   ETHER-  ON  THE 

GENOUS       EX-  N-FREE  DRY  MA- 

WATER.     MATTER.  TRACT.  SUGAR.  MATTER.  FIBER.  ASH.    TERIAL. 

Chicory,  roasted,  .  13.16  6.53  2.74  17.89  41.42  12.07  6.19  70.50 
Figs,  roasted,  .  .  .  12.50  4.57  2.96  32.50  31.92  12.34  5.21  82.50 
St.  John's  bread  v— v— ' 

(Carobbean),      .    5.35       8.93       365  69.83  10.15     2.09     63.71 

Cereals  (rye,  etc.),  .  12.50     12.15       3.57       4.12     55.66       8.45     3.55     48.53 

Malt, 7.08     13.05       2.25     15.67     51.74       7.38     2.83     65.00 

Mogdad  coffee  ( Cas- 
sia   occidentalis},  11.09     I5-I3       2-55  46.69  21.21     4.33     30.00 
"Congo"    coffee, 

raw, 13.72     39.82       1.26  37.09  4.41     3.70 

"Congo"    coffee, 

roasted,    ....    4.22     27.06       1.19       3.25     39.74     19.28     4.63     22.50 
Acorns,  shelled  and 

roasted,    ....  12.50       6.78       4.35  69.27  5.02     2.07     28.88 

Date  stones   (Phce- 

nix   dactyliferd],    9.27       5.46       8.50  52.86  23.97     1.44     12.87 

Fruit  of  wax  palm, 

raw, 9.37       6.54     10.57        1.67     25.48     44.31     2.06     13.41 

Fruit  of  wax  palm, 

roasted,    ....     3.76       6.99     14.06       1.25     33.25     38.45     2.24     14.03 

A  number  of  methods  have  been  proposed  for  the  deter- 
mination of  the  caramel  in  coffee  roasted  with  sugar.  A 
method  due  to  Hilger  is  as  follows  :  10  grams  of  the  whole 
coffee  are  shaken  for  half  an  hour  each  time  with  three  suc- 
cessive portions  of  100  c.c.  of  a  mixture  of  equal  parts  ot 
water  and  85  per  cent,  alcohol.  The  united  solutions  are 
made  up  to  500  c.c.,  filtered,  the  residue  dried  at  100°, 
weighed,  and  the  ash  determined  and  deducted.  It  is  neces- 
sary to  decant  the  liquid  from  the  berries  before  filtering, 
since  the  extra  time  considerably  increases  the  relative  amount 
of  ash  in  the  extract,  due  to  the  more  complete  extraction  of 
the  constituents  of  the  berry  itself.  Fresenius  and  Griinhut 
consider  that  the  best  results  are  had  by  deducting  from  the 
result  a  mean  constant  for  the  materials  extracted  from  the 
coffee  itself. 


COFFEE 


273 


The  following  results  were  obtained.  The  roasting  of  the 
coffee  without  sugar  was  performed  in  the  normal  manner ; 
i.  e.y  the  loss  on  roasting  was  about  18  per  cent.  : 

SOLUBLE  RESIDUE 
(LESS  ASH). 

Yellow  Java, 0.71 

Green       "       0.62 

Blue         " 1.39 

Maracaibo,      0.60 

Average, .*  ...  0.83 


Yellow  Java  roasted  with  7^  per  cent,  of  sugar, 

9 
Green 


Blue 


Maracaibo 


9 

7/2 

9 


PERCENTAGE  OF  ASH- 
FREE  SOLUBLE  MATTER 
LESS  0.83. 

.  .  .  2.21 

.  .  .2.83 

.  .  .  2.06 

.  .  .  3.46 

•  •  •  2-55 
.  .  .  4.00 
.  .  .  2.78 

•  •  •  3-39 


Coffee  Extracts. — Many  attempts  have  been  made  to  pre- 
pare a  concentrated  infusion  of  coffee,  but  the  results  have 
not  been  satisfactory.  In  most  cases  preservatives  are  neces- 
sary. Some  preparations  contain  excessive  proportions  of 
sugar,  and  occasionally  caffein  is  added  to  enrich  the  mixture. 
C.  G.  Moor  and  M.  Priest  3  2  give  the  following  analyses  of 
English  preparations : 

TOTAL  SOLIDS.     ASH.  NITROGEN.    CAFFEIN. 

Coffee  extract, 39.9  4.25  0.96  1.98 

27.9  0.95  0.15  0.47 

with  chicory,    .  30.0  0.36  .    .  0.32 

34.8  1.28  0.23  0.54 

46.4  0.43  0.06  0.57 

with  chicory,    .  37.6  0.36  .    .  0.02 
50.6  0.55  0.41  0.56 

with  chicory,    .  48.6  1.87  0.37  0.26 

"     sugar,    .    .  51.5  2.50  0.38  0.61 

"     chicory,    .48.5  1.14  0.30  0.28 


In  the  first  sample  caffein  has  probably  been  added. 
Essence  of  Coffee. — Coarsely  broken  cereals  roasted  with 


2/4  FOOD    ANALYSIS 

molasses  have  sold  under  this  title.  The  nature  of  the 
material  may  usually  be  determined  by  simple  inspection.  Of 
late  years,  the  term  "  essence  for  coffee  "  has  been  substituted. 


CACAO  AND  CHOCOLATE 

Cacao  is  prepared  from  the  seeds  of  Theobroma  cacao  L. 
The  fruit  contains  from  25  to  40  slightly  flattened  ovate 
seeds,  1.5  to  2.5  cm.  long  and  0.6  to  1.5  cm.  broad,  which 
are  colorless  when  first  removed  from  the  pulp,  but  become 
yellow,  red,  or  brown  on  exposure.  They  are  dried  in  the 
sun,  either  at  once  or  after  being  subjected  to  fermentation 
(brought  about  in  some  cases  by  burial),  which  removes  the 
pulp  and  much  of  the  acridity  and  bitterness. 

Cacao  seeds  contain  theobromin,  cafifein,  fat,  tannin,  starch, 
gum,  proteids,  and  tartrates.  The  taste  and  odor  are  due  to 
volatile  materials  developed  in  roasting. 

Theobromin,  dimethylxanthin,  crystallizes  in  colorless, 
minute,  rhombic  needles.  One  part  is  soluble  in  the  follow- 
ing parts  of  solvents  :  cold  water,  1600  ;  boiling  water,  148  ; 
cold  alcohol,  4280;  boiling  alcohol,  400;  cold  ether,  1700  ; 
boiling  ether,  600  ;  boiling  chloroform,  105.  It  is  insoluble 
in  petroleum  spirit.  It  dissolves  in  acid  and  alkaline  solu- 
tions, especially  in  ammonium  hydroxid,  and  is  completely 
extracted  from  alkaline  solution  by  chloroform.  When  the 
solution  in  ammonium  hydroxid  is  mixed  with  silver  nitrate 
and  heated  for  a  considerable  time,  a  silver  compound  is  pre- 
cipitated. 

W.  E.  Kunze  has  examined  the  methods  for  the  separation 
of  the  alkaloids,  and  found  all  defective.  In  estimating  the 
alkaloids  of  cacao  previous  removal  of  the  fat  is  not  advisable, 
as  some  alkaloid  is  extracted.  Kunze  recommends  the  fol- 
lowing process  :  The  material  is  boiled  for  30  minutes  with 
normal  sulfuric  acid,  filtered,  and  a  large  amount  of  a  solu- 


CACAO    AND   CHOCOLATE  275 

tion  of  sodium  phosphomolybdate  in  nitric  acid  added.  The 
precipitate,  which  usually  settles  rapidly,  is  removed  by  filtra- 
tion after  24  hours,  washed  with  dilute  sulfuric  acid,  and  at 
once  decomposed  by  treatment  with  barium  hydroxid  solu- 
tion, the  excess  of  barium  hydroxid  being  removed  by  carbon 
dioxid.  The  liquid  and  precipitate  are  evaporated  to  dryness 
and  the  residue  extracted  with  boiling  chloroform.  The 
chloroform  solution,  on  evaporation,  leaves  the  alkaloids 
almost  perfectly  pure,  and  containing  only  a  trace  of  ash. 

Separation  of  the  alkaloids  may  be  effected  by  converting 
the  theobromin  into  a  silver  compound.  The  mixture  of  alka- 
loids is  dissolved  in  ammonium  hydroxid,  a  considerable  ex- 
cess of  nitrate  is  added,  the  solution  boiled  down  to  small  bulk, 
and  until  all  free  ammonia  is  expelled.  The  crystalline  pre- 
cipitate is  collected,  washed  with  boiling  water,  ignited,  and 
the'  metallic  silver  weighed.  The  process  may  be  made  vol- 
umetric by  titrating  the  excess  of  silver  in  the  filtrate  by 
Volhard's  method.  In  the  latter  case  the  alkaloids  may  be 
readily  isolated  from  the  precipitate  and  the  filtrate  (after  titra- 
tion),  and  tested  as  to  their  purity,  identity,  etc.  The  sepa- 
ration of  caffein  from  theobromin  by  means  of  benzene  is 
imperfect. 3  3 

The  proportions  of  theobromin  given  by  different  observers 
differ  greatly,  owing  in  part  to  the  methods  employed.  The 
average  of  the  reported  data  is  about  1.5  per  cent.  Kunze 
found  by  his  method  1.2  per  cent,  total  alkaloids.  Weigmann 
obtained  the  following  results  : 

BEANS.  HUSKS. 

Theobromin,  per  cent., 1.26  0.50 

Caffein,  per  cent., 0.17  0.15 

Sodium  phosphomolybdate  solution  is  prepared  as  follows  : 
A  warm  solution  of  disodium  hydrogen  phosphate  is  acidu- 
lated with  nitric  acid  and  an  excess  of  ammonium  molybdate 
solution  added.  The  precipitate  is  washed  with  water  con- 


2/6  FOOD    ANALYSIS 

taining  nitric  acid  and  dissolved  in  a  hot  solution  of  sodium 
carbonate.  The  liquid  is  evaporated  to  dryness,  the  residue 
ignited  at  a  low  red  heat  until  all  ammonium  is  volatilized, 
moistened  with  nitric  acid,  and  again  ignited.  I  gram  of  the 
product  is  dissolved  in  10  c.c.  of  water  and  I  c.c.  of  nitric 
acid  (sp.  gr.  1.42)  added. 

According  to  Stutzer,  the  nitrogenous  constituents  of  cacao 
are  of  three  types  : 

1.  Non-proteids,    not    precipitated    by    copper    hydroxid 
(theobromin,  caffein,  and  amido-compounds). 

2.  Digestible  albumin,  insoluble  in  pure  water  in  presence 
of  copper   hydroxid,   but  soluble  when  treated  successively 
with  acid  gastric  juice  and  alkaline  pancreatic  extract. 

3.  Insoluble  and  indigestible  nitrogenous  matter. 

He  gives  analyses  of  three  samples,  showing  the  relative 
proportion  of  these  forms  : 

Nitrogen  as  soluble  compounds,  in- 
cluding that  of  alkaloids,      .    .    .3143  26.95  29.79 
Nitrogen  as  digestible  albumin,   .    .  33.34  40.61  22.62 
Nitrogen  as  indigestible  mattei',  .    -35-33  32-44  47- 83 

100.00       100.00       100.00 

Fat. — The  so-called  cacao-butter  is  a  yellowish-white  solid, 
of  pleasant  odor,  melting  between  28°  and  30°.  Further 
data  in  regard  to  it  are  given  in  connection  with  the  fats. 

Cacao-red. — This  appears  to  be  an  oxidation  product  of  the 
tannin.  It  does  not  exist  as  such  in  the  cacao.  It  may  be 
prepared  from  the  aqueous  or  alcoholic  decoction  by  pre- 
cipitating with  lead  acetate  and  decomposing  the  washed 
precipitate  with  hydrogen  sulfid.  The  colorless  liquid  so 
obtained  becomes  red  on  evaporation.  Cacao-red  is  slightly 
soluble  in  cold  water,  much  more  so  in  hot. 

Gum.— About  2  per  cent,  of  gum  is  present.  It  is  pre- 
cipitated by  alcohol  from  the  watery  extract  of  the  fat-free 
cacao.  It  resembles  gum  arabic,  but  is  dextrorotatory. 


CACAO    AND    CHOCOLATE 


277 


Tartaric  Acid. — This  has  been  found  to  be  present  to  the 
extent  of  several  per  cent.  Weigmann  estimates  it  by  neu- 
tralizing the  aqueous  extract  with  ammonium  hydroxid,  add- 
ing calcium  chlorid,  redissolving  the  precipitate  in  hydro- 
chloric acid,  and  reprecipitating  with  sodium  hydroxid.  From 
4.34  to  5.82  per  cent,  of  tartaric  acid  were  found  in  this  way. 

Starch. — The  granules  of  cacao-starch  are  very  small  ; 
their  microscopic  characters  are  given  on  page  95.  Samples 
of  cacao  examined  by  E.  E.  Ewell  contained  from  5.78  to 
15.13  per  cent,  of  starch. 

Mineral  Matter. — The  ash  of  cacao  consists  largely  of 
phosphates  with  but  little  chlorids  and  carbonates.  The 
amount  of  magnesium  exceeds  notably  that  of  the  calcium. 
The  proportion  of  sodium  is  small,  and  traces  of  copper  are 
usually  present.  The  following  are  some  analyses.  The 
proportion  of  husk  ranges  from  8  to  1 5  per  cent.  : 

ANALYSES  BY  J.  BELL 


m 

PER  100  OF 
CACAO. 

PER  100  OF  ASH. 

Water. 

Ash  (on 

Sub- 
stance). 

Soluble 
in 
Water. 

Insol. 
in 
Acid. 

Phos- 
phoric 
Oxid. 

Carbon 
Dioxid. 

Potas- 
sium 
Oxid. 

Fer- 
rous 
Oxid. 

Guayaquil  nibs  (i. 
f.,  husked),   .    . 

5.06 

3-63 

56-3 

None 

49-4 

0.69 

23-4 

0.21 

Surinam  nibs,    .    . 

4-55 

2.90 

43-5 

None 

378 

3-31 

28.0 

0.38 

Grenada  nibs,   .    . 

5-71 

2.82 

48.6 

None 

39-2 

2.92 

27.6 

0.15 

Finest  Trinidad 
nibs,        .... 

4-47 

2-75 

46.6 

None 

36.2 

4.19 

29-3 

0.  II 

Finest  Trinidad 
husks,     .... 

10.19 

8.63 

54-9 

5-91 

17.2 

10.8 

37-9 

0.63 

The  important  commercial  cacao  preparations  are  : 

Plain  chocolate,  which  consists  of  the  roasted  and  husked 


2/8 


FOOD    ANALYSIS 


seeds,  ground  to  a  paste  while  quite  hot  and  pressed  into  cakes. 
This  is  known  in  Europe  as  "  cacao  masse." 


ANALYSES  BY  H.  WEIGMANN 


MOIS- 
TURE. 

NITRO- 
GENOUS 
MATTER. 

THEO- 

BROMIN. 

FAT. 

STARCH. 

OTHER 
NITRO- 
GEN-FREE 
MATTER. 

FIBER. 

ASH. 
4.61 

Raw,  unhusked, 

7-93 

14.19 

1.49 

45-57 

5-85 

17.07 

4-78 

Roasted,    " 

6.79 

14.13 

I.58 

46.19 

6.06 

18.04 

4.63 

4.16 

"         husked 
(nibs),      .    .    . 

5.58 

14.13 

i-55 

50.09 

8.77 

I3-91 

3-93 

3-59 

Cacao    masse, 
(plain   choco- 
late),   .... 

4.16 

13-97 

1.56 

53-°3 

9.02 

12.79 

3-40 

3.63 

Husks  (contained 
4.06  per  cent, 
sand),  .... 

n-73 

13-95 

0-73 

4.66 

^^—  -— 
43 

--—  —_  -•' 
.29 

16.02 

10.71 

Sweet  chocolate  is  the  mixture  of  the  above  with  50  per  cent. 
or  more  of  sugar,  and  flavoring  materials,  such  as  spices  and 
vanilla. 

Cacao  essence,  or  cacao  powder,  is  prepared  by  removing 
from  the  husked  and  roasted  bean,  by  means  of  heat  and 
pressure,  a  portion  (usually  about  one-half)  of  the  fat. 

The  so-called  soluble  "  cocoas  "  are  prepared  by  treating  the 
above  with  ammonium  hydroxid,  sodium  carbonate,  or  steam 
to  destroy  the  cellular  structure,  to  convert  the  proteids  into 
more  soluble  modifications,  but  more  especially  to  emulsify 
the  fat  so  that  it  may  not  come  to  the  surface  when  the 
decoction  is  made.  The  treatment  with  sodium  carbonate  is 
practised  by  the  Dutch  manufacturers.  The  term  soluble  in 
connection  with  such  preparations  is  not  justified,  as  is  evident 
from  the  following  analyses  made  by  Stutzer  : 

I.  Made  from  a  mixture  of  Ariba,  Machala,  and  Bahia 
cacao  without  the  use  of  chemicals. 


CACAO    AND    CHOCOLATE  2?9 

II.   Dutch  cacao. 

Ill  and  IV.   German  cacao  prepared,  in  Stutzer's  opinion, 
by  the  use  of  ammonium  hydroxid. 

I.  II.  III.               IV. 

Water 4.30  3.83  6.56           5.41 

Fat, 27.83  30.51  27.34  33.85 

NUreogen-freeext;act,'    !   *   ."    !    !    !   .*  i    .'38:62}  37-48  39-99  36.06 

Total  nitrogenous  substances  ( I ), 20.84  19.88  20.93  J9-25 

Ash  (2), 5.05  8.30  5  18           5.43 

(1)  Total  nitrogen,      3.68  3.30  3.95           3.57 

Theobromin, 1.92  1.73  1.98            1. 80 

Ammonia, 0.06  0.03  0.46           0.33 

Amido-compounds, 1.43  1.25  0.31            I.  U 

Digestible  albumin,              .        .    .10.25  7-°^  10.50           7.81 

Indigestible  nitrogenous  matters,  .^  7.18  9.19  7.68           8.00 

Containing  nitrogen, 1.15  1.47  1.23            1.28 

Proportion  of  total    nitrogen  indi- 
gestible,      31.2  44.5  32.2  35.8 

(2)  Phosphoric  oxid, 1.85  2.52  2.14           2.05 

"             "    soluble  in  water,  .     1.43  0.50  0.74           0.77 

Ash  soluble  in  water, 3.76  4.76  2.86           2.76 


Stutzer  considers  that  the  addition  of  alkalies  is  unneces- 
sary, since  the  best  results  may  be  had  from  the  untreated 
bean,  if  the  preparation  and  roasting  be  properly  conducted. 

ADULTERATIONS. — The  finest  grades  of  cacao  are  made 
from  the  cotyledons  only.  The  husks  are  occasionally  added 
to  the  cheaper  grades  of  chocolate.  On  account  of  the  large 
proportion  of  fat  in  cacao  (usually  about  50  per  cent.),  it  is 
impossible  to  prepare  from  it  a,  permanent  powder  unless  a 
part  of  the  fat  be  removed  or  a  diluent  such  as  starch  or 
sugar  be  added.  In  many  cases  more  than  half  of  the  fat  is 
allowed  to  remain.  The  common  adulterants  of  cacao  pow- 
der are  sugar,  starches,  and  flours.  The  color  of  the  diluted 
material  may  be  improved  by  the  addition  of  ferruginous 
mixture  or  artificial  colors.  Copper  sulfate,  potassium  chro- 
mate,  and  nickel  sulfate  are  said  to  have  been  added.  Choc- 
olate is  often  adulterated  with  ground  peanuts,  almond  cake, 
and  similar  material.  In  some  cases  a  portion  of  the  fat  is 


28O  FOOD    ANALYSIS 

removed  and  foreign  fat  substituted.  Finely  divided  tin  is 
stated  to  have  been  added  in  order  to  impart  a  metallic  luster. 

ANALYTIC  METHODS. — A  careful  examination  under  the 
microscope  should  be  made  in  order  to  determine  the  pres- 
ence of  husks,  foreign  starches,  peanut,  almond,  or  other  ad- 
ditions. A  determination  of  the  ash,  and  of  its  solubility  and 
alkalinity,  should  be  made.  The  ash  of  pure  cacao  is  white, 
and  usually  under  4  per  cent.,  if  prepared  from  the  cotyledons 
only.  A  higher  proportion  may  point  to  the  presence  of 
husks,  added  mineral  matter,  or  the  use  of  alkali  in  the 
manufacture.  (See  tables,  pp.  278  and  279.)  The  moisture 
and  fat  should  be  determined  as  on  pages  36  and  50.  The 
extraction  of  the  fat  should  be  performed  by  means  of  petro- 
leum spirit.  The  material  extracted  may  be  examined  for 
foreign  fats  as  described  on  page  183.  In  the  case  of  cacao 
prepared  by  the  use  of  alkali  an  appreciable  amount  of  soap 
will  be  present,  which  will  remain  undissolved  by  the  petro- 
leum spirit.  It  may  be  separated  by  treating  the  residue 
with  alcohol  acidified  with  hydrochloric  acid,  evaporating  to 
dryness,  and  shaking  with  water  and  ether.  The  fatty  acids 
are  recovered  from  the  ether  by  evaporation. 

The  determination  of  the  theobromin  and  caffein  may  be 
made  as  described  on  page  274.  The  determination  of  total 
nitrogen  is  easier.  The  following  analyses  by  A.  Bitteryst 
show  the  use  of  such  determination  : 

PERCENTAGE  OF  PROTKIDS. 

Pure  chocolate, 9.10 

"     cacao, 17-57 

Peanuts, 28.18 

Peanut-cake, 46.90 

Pure  chocolate  -j-  10  per  cent,  of  peanuts,    .    .    .    .    .    .12.53 

"  "         -f-  10       "          peanut-cake, 15.70 

"      cacao        -f  I0       "  "  2I-lS 

Sugar. — Exact  determinations  of  sugar  are  difficult,  but 
approximations  quite  sufficient  for  practical  purposes  may  be 
made  by  the  polarimeter.  The  gum  introduces  an  error 


CACAO    AND    CHOCOLATE  28 1 

ranging  from  0.3  to  2.0  per  cent.  To  avoid  interference  from 
starch,  the  solution  must  be  made  with  cold  water.  E.  E. 
Ewell  has  found  that  it  is  necessary  to  use  about  40  c.c.  of 
water  for  each  gram  of  sample.  The  following  process, 
described  by  Ewell,34  is  adapted  to  a  polarimeter  requiring 
a  concentration  of  26.048  grams:  13.024  grams  of  material 
are  triturated  with  alcohol  to  a  smooth  paste,  which  is  trans- 
ferred to  a  500  c.c.  flask,  diluted  with  400  to  450  c.c.  of 
water,  and  shaken  occasionally  during  four  hours  ;  after  which 
10  c.c.,of  a  saturated  solution  of  lead  acetate  are  added,  the 
volume  brought  to  500  c.c.,  and  allowed  to  stand  for  one  hour, 
with  occasional  shaking.  The  solution  is  filtered  and  the 
polarimetric  reading  taken  in  a  4-decimeter  tube.  Under 
these  conditions  the  reading  is  reduced  to  one-fifth,  and  if  the 
instrument  is  graduated  in  ordinary  sugar  degrees  the  read- 
ing, multiplied  by  5,  will  give  results  close  enough,  since 
there  is,  as  noted  above,  an  indefinite  error  from  the  gum  in 
solution.  Ewell  prefers  to  allow  for  the  volume  of  the  pre- 
cipitate, and  has  given  a  formula  which,  reduced  to  a  simpler 
form  than  as  he  presents  it,  is  : 

Percentage  of  sugar  =  4.88  R  -f-  0.0065  R2  ;  R  being  the  observed  reading. 

Starch. — This  is  determined  by  the  method  given  on  page 
97,  the  sugar  being  first  removed  by  cold  water. 

Crude  Fiber. — This  is  determined  as  on  page  46.  Little 
reliance  can  be  placed  upon  many  published  figures  for  this 
datum,  on  account  of  the  differences  in  methods  employed. 

As  a  means  of  detecting  the  use  of  alkalies  in  the  manu- 
facture of  cacao  the  following  data  may  be  determined  : 
Total  ash,  water-soluble  ash,  total  phosphate  and  that  in  the 
cold  water  solution,  expressed  as  phosphoric  oxid.  The 
relative  proportions  of  these  constituents  in  the  ash  of  normal 
cacao  and  of  cacao  treated  with  fixed  alkalies  and  ammonia 
are  given  in  the  table  on  page  279.  Additional  evidence  of  the 
use  of  ammonia  is  obtained  by  distillation  of  the  sample  with 


282 


FOOD    ANALYSIS 


magnesia  and  determination  of  the  ammonia  in  the  distillate. 
If  this  process  yields  more  than  o.  I  per  cent,  of  nitrogen  in 
the  form  of  ammonia,  Stutzer  considers  the  result  certain 
evidence  of  the  use  of  ammonia  or  ammonium  salts  in  the 
manufacture. 

The  following  table  gives  some  of  the  results  obtained  by 
E.  E  Ewell  from  an  examination  of  cacao  preparations  as 
found  in  the  American  market : 


FOREIGN 
STARCHES. 

WATER 

FAT. 

CANE- 
SUGAR 

BY 

POLAR. 

CRUDE 
FIBER. 

TOTAL 
ASH. 

N  . 
—  ACID 
10 
REQ.  TO 
NEU- 
TRAL- 
IZE 
ASH  OF 
i  GRAM. 

Plain  Chocolates  : 

p.  c. 

p.  c. 

p.  c. 

p.  c. 

p.  c. 

c.c. 

Chocolate,      .    . 

None. 

3-18 

50.84 

•    • 

2.91 

3-44 

2-55 

Much  wheat 

starch. 

3-09 

49.81 

.    . 

2-63 

3.08 

2.12 

Much  wheat 

• 

flour. 

3-82 

49.40 

.    . 

2.74 

3.18 

2.30 

Sweet  Chocolates  : 

"Instantaneous 

Chocolate,"    . 

None. 

1.88 

24.04 

53 

1.32 

1.69 

1-45 

"Powdered,"    . 

None. 

i-55 

17-73 

65 

0.94 

I.  21 

0.75 

"  Princess,"   .    . 

None. 

1.46 

25-74 

55 

1.14 

i-54 

0.92 

"Vanilla,"    .    . 

None. 

0.65 

22.49 

57 

1.23 

1.52 

I.OO 

Cocoas  and  Bromas: 

Breakfast  Cocoa, 

None. 

25.83 

.   . 

4-23 

5-05 

3-65 

Cocoa  Extract,  . 

None. 

•   • 

30-95 

.   . 

3-89 

4.24 

2-9 

Dutch  Cocoa, 

None. 

•   • 

31.48 

.   . 

3.76 

6.06 

4.8 

Breakfast  Cocoa, 

Wheat    flour 

and  arrow- 

root. 

•   . 

35.85 

•   • 

3.08 

3-84 

2.6 

Prepared  Cocoa, 

Much  arrow- 

root. 

•   • 

25-94 

26 

«-5« 

3-15 

i-3 

VINEGAR  283 

CONDIMENTS   AND    SPICES 

VINEGAR 

Vinegar  is  the  acid  liquid  resulting  from  the  acetous  fer- 
mentation of  various  decoctions  or  fruit  juices.  Acetic  acid 
is  the  prominent  constituent,  but  small  amounts  of  alcohol, 
aldehyde,  and  ethyl  acetate  are  usually  present,  together  with 
extractive  matters  depending  upon  the  nature  of  the  material 
used.  Very  dilute  solutions  of  acetic  acid  do  not  keep  well, 
and  the  presence  of  a  little  alcohol  is  regarded  as  desirable, 
improving  the  flavor  and  keeping  qualities.  Some  mineral 
acid  was  formerly  thought  to  be  necessary  as  a  preservative. 
Such  addition  is  not  needed,  and  is  now  sometimes  practised 
as  an  adulteration.  Sulfuric  acid  is  usually  employed,  rarely 
hydrochloric. 

Vinegar  is  often  made  by  spontaneous  fermentation,  but 
malt  and  spirit  vinegars  are  mostly  made  by  passing  a  dilute 
alcohol  over  beech-shavings  or  birch-twigs,  impregnated  with 
the  acetic  ferment,  principally  Mycoderma  aceti,  a  regulated 
supply  of  air  being  maintained  at  the  same  time.  The  con- 
version of  the  alcohol  into  acetic  acid  takes  place  rapidly. 

Wine,  cider,  malt,  and  spirit  vinegar  are  the  chief  forms. 

Wine  Vinegar. — That  from  white  wine  is  most  esteemed. 
It  usually  contains  between  5  and  10  per  cent,  of  acetic  acid, 
1.5  and  3  per  cent,  of  solids,  and  0.2  and  0.6  per  cent,  of  ash. 
The  extract  contains  from  0.25  to  0.5  per  cent,  of  acid  potas- 
sium tartrate.  The  following  analyses  of  true  vinegar  result- 
ing from  four  months'  fermentation  are  by  K.  Farnsteiner  : 


I.                      2.  3. 

Alcohol, 3.75  o.oo  1.23 

Acid, 3.56  7.60  6.00 

Solids, 2.03  3.64  2.56 

Ash, 0.28  0.30  0.34 

Alkalinity  of  ash  inc.  c.  of  normal  alkali,  1.78  2.90  2.85 


284 


FOOD    ANALYSIS 


Small  amounts  of  sugar,  glycerol,  and  tartaric  acid  are  pres- 
ent in  each  sample. 

In  the  United  States,  spirit  vinegar  made  from  the  dilute 
alcohol  called  "  low  wine"  is  commonly  sold  as  white  wine 
vinegar. 

Cider  vinegar  is  a  brownish  liquid  containing  about  4  per 
cent,  of  acetic  acid  and  2  per  cent,  of  solid  matter  which  has 
the  odor  and  taste  of  apples.  It  is  frequently  imitated  by 
spirit  vinegar  or  diluted  acetic  acid  colored  with  caramel.  G. 
S.  Cox  and  A.  W.  Smith  have  published  analyses  of  commer- 
cial cider  vinegars.  The  former  found  in  20  samples  a  per- 
centage range  of  acidity  from  2.3  to  8.4,  solids  1.34  to  4,  ash 
0.25  to  0.52.  Smith  examined  51  samples,  22  of  which  were 
genuine,  27  diluted  with  water  or  spirit  vinegar,  one  made  from 
dried  apples  and  glucose,  and  one  made  from  cider  and  grape - 
juice.  The  following  table  shows  the  differences  in  important 
data  : 


GRAMS  PER 
100  GRAMS  OF  VINEGAR  : 


MILLIGRAMS  PER 
TOO  GRAMS  OF  VINEGAR: 


A    -A  Phosphoric  Phosphoric 
7  Acid      Oxid  in         Oxid  in 
Required    Soluble        Insoluble 


Acid. 

Solids. 

Ash. 

for  Ash. 

Ash. 

As 

Maximum,      .    .7.61 

4-45 

0.51 

55-2 

22.7 

19.4 

Minimum,  .    .    .3.24 

2.OO 

0.3I 

28.4 

13-6 

4-2 

Average,     .    .    .4.46 

2.83 

o-39 

38.8 

I9.I 

10.  1 

Cider  vinegar  di- 

luted    with 

water    or 

spirit    vine- 

gar: 

Maximum,      .  4.83 

3-41 

0-53 

29.6 

15-2 

20.2 

Minimum,       .  3.01 

I.I9 

0.14 

1.4 

0.00 

3-0 

Average,     .    .4.00 

2.03 

0.24 

18.4 

5-2 

5-7 

Sample     from 

dried     apples 

and  glucose,  .  4.29 

3^9 

0.25 

21.0 

Sample    from 

cider     and 

grape-juice,    .  4.54 

2.77 

0.30 

34-o 

Smith  finds  that  the  ash  of  cider  vinegar  begins  to  melt  and 
volatilize    at   a  comparatively  low  temperature  and  gives   to 


VINEGAR  285 

flame  the  potassium  color  unobscured  by  that  of  sodium.  It 
is  low  in  chlorids  and  sulfates  and  high  in  carbonates  and 
phosphates ;  about  two-thirds  of  the  phosphates  are  soluble 
in  water.  In  the  ash  of  other  vinegars  a  much  lower  propor- 
tion of  phosphates  is  soluble  in  water.  The  dilution  of  vine- 
gar by  natural  water  will  be  apt  to  reduce  the  soluble  matter 
by  the  formation  of  calcium  and  magnesium  phosphates. 
Manufacturers  occasionally  add  potassium  phosphate  to  di- 
luted cider  vinegars  to  correct  deficiency. 

Pure  cider  vinegar  gives  no  polarimetric  rotation  after  clari- 
fication with  lead  acetate.  The  addition  of  this  reagent  de- 
colorizes the  liquid,  producing  a  flocculent  brownish  precipi- 
tate. 

Spirit  Vinegar. — This  is  made  by  distilling  a  fermented 
mash  of  grain  so  as  to  obtain  a  very  dilute  alcohol,  techni- 
cally called  "  low  wine,"  which  is  converted  without  rectifica- 
tion or  concentration  into  vinegar  by  the  "  quick  "  method 
above  described.  Spirit  vinegar  is  often  colored  with  cara- 
mel to  simulate  cider  or  wine  vinegar.  Pure  spirit  vinegar 
on  evaporation  leaves  but  a  small  amount  of  solids  and  a 
trace  of  ash.  The  following  is  a  summary  of  the  results 
obtained  by  A.  W.  Smith  in  the  examination  of  65  samples 
of  spirit  vinegar  : 

AVERAGE. 

Acetic  acid, 2.87105.99  3.84 

Total  solids, 0.14  "0.78  0.38 

Ash, o.oi  "  0.15  0.06 

The  ash  had  a  very  slight  alkalinity  and  only  traces  ot 
phosphates. 

Malt  Vinegar. — This  is  characterized  by  a  comparatively 
large  amount  of  nitrogenous  matter.  The  following  table 
exhibits  the  usual  composition  as  contrasted  with  vinegar 
prepared  from  glucose  and  sucrose.  The  water  used  in  the 
preparation  of  the  mash  may  have  much  influence  on  the  com- 


286 


FOOD    ANALYSIS 


position  of  the  ash.  According  to  Sykes,  various  yeast-foods 
containing  phosphates  are  often  added  to  the  wort  with  a  view 
to  stimulate  the  yeast  and  secure  a  higher  production  of 
alcohol. 


ANALYST,    .           .    . 

A  W  SMITH 

A    H    ALLEN 

CHARACTER  OF 
VINEGAR. 

MALT, 
4  SAMPLES. 

MALT, 
4  SAMPLES. 

CHIEFLY  FROM  RICE 
HYDROLYZED  BY 
SULFURIC  ACID. 

FROM 
SUGAR. 

Per  100  parts  of  vinegar  : 

Per  Cent. 

Grams  per 
100  c.c. 

Grams  per  loo  c.c. 

Gms.  per 

100  C.C. 

Acetic  acid,  .... 

4.01  to  5.90 

4.86  to  6.6l 

5.58 

5-7o 

4.92 

Total  solids,     .    .    . 

1.75  to  2.67 

2.31  to  3.96 

2.98 

2.09 

I.76 

Ash 

o  20  to  o  28 

O  34.  to  O  US 

O  3O 

O  4.3 

o  278 

"      alkalinity, 

O.O2  to  O.O26 

0.091  to  0.118 

0.13 

Phosphoric  oxid,     .    . 

0.09  to  0.125 

0.057  to  0093 

0.017 

0.024 

0.016 

Nitrogen,     .... 

Not  det. 

0.095  to  0.120 

0.104 

O.O62 

0.016 

"  Original  solids,"  . 

7.76  to  1  1.  06 

9.60  to  12.73 

"•35 

10.64 

IO.O2 

A  form  of  malt  vinegar  often  sold  is  made  by  acidifying 
dilute  alcohol  by  the  quick  process  and  coloring  the  liquid  by 
steeping  in  it  a  strongly  scorched  malt.  This  form  contains 
less  phosphates  and  solid  matter  than  the  true  malt  vinegar. 
Another  method  is  the  use  of  so-called  "malt  acid,"  "vine- 
gar extract,"  or  "vinegar  essence,"  obtained  by  fermenting 
potato  spirit  with  the  Mycoderma  aceti,  neutralizing  the  acetic 
acid  with  lime,  and  distilling  the  resulting  calcium  acetate  with 
an  acid.  This  product  may  contain  from  40  to  90  per  cent, 
of  acetic  acid.  The  fermented  potato  spirit,  containing  as 
much  as  13  per  cent,  of  acetic  acid,  is  also  sold  under  the 
name  "  Essig  sprit"  or  "spirit  vinegar."  The  following 
analyses  are  due  to  A.  H.  Allen  and  C.  G.  Moor : 


VINEGAR 


287 


"  ESSIG 
SPRIT." 

"MALT  ACID." 

Acetic  acid,   

Gr 
11.26 
0.64 
0.06 

ams  per  100  ( 
88.02 
2.77 
0.15 

:.c. 
45-4 
12.14 
0.18 

0.017 
0.113 

0.074 

Total  solids,      ....                ...        ... 

Ash,   ,  

Alkalinity  of  ash  as  potassium  oxid,  

Phosphorus,       

Trace 
0.014 

Nitrogen,   

Sulfuric  acid  (free),  

Commercial  vinegars  are  made  from  these  products  by 
dilution  with  water  and  adding  coloring  and  flavoring 
materials.  According  to  Allen  and  Moor,  it  is  the  practice 
of  some  manufacturers  to  distil  a  portion  of  the  product, 
reserve  the  stronger  portion  of  the  distillate  for  sale  as  distilled 
vinegar,  and  add  the  weaker  fractions  to  some  of  the  undis- 
tilled  article.  Distilled  malt  vinegar  contains  appreciable 
amounts  of  alcohol,  ethyl  acetate,  furfural,  and  aldehyde,  and 
has  a  highly  characteristic  taste  and  odor. 

"  Original  Solids." — O.  Hehner  has  called  attention  to  the 
fact  that  additional  information  as  to  the  nature  of  a  vinegar 
may  be  obtained  by  calculating  the  weight  of  materials  prior 
to  fermentation.  90  parts  of  glucose  should  produce -60 
parts  of  acetic  acid  ;  therefore  the  amount  of  acetic  acid  in 
the  sample,  multiplied  by  1.5  and  added  to  the  solids,  will 
give  the  figure  termed  by  Hehner  "  original  solids."  The 
loss  of  acetic  acid  during  fermentation  may,  however,  be  as 
much  as  50  per  cent,  and  the  figure,  therefore,  will  be  only 
an  approximation,  but  it  is  often  instructive.  The  following 
table  shows  the  method  applied  to  the  twenty-two  samples 
of  cider  vinegar  given  on  page  284. 


288  FOOD    ANALYSIS 


Maximum, 
Minimum, 

SOLIDS  +  1.5 
ACETIC  ACID. 

.    .    .       14.38 
.    .    .    .     7.63 

MILLIGRAMS  OF 
ASH  PER  100  GRAMS 
ORIGINAL  SOLID. 

6.09 
2-73 

MILLIGRAMS    OF 
PHOSPHORIC  OXID 
PER  100  GRAMS 

OF  0.   S. 

3-77 
1.72 

Average, 9.65  4.11  3.10 

ANALYTIC  METHODS. 

Acetic  Acid. — This  may  be  determined  with  sufficient  accur- 
acy by  diluting  5  c.c.  of  the  vinegar  with  50  c.c.  of  water 
and  titrating  with  standard  alkali,  using  phenolphthalein  as 
indicator. 

Total  Solids. — 5  c.c.  of  the  vinegar  are  evaporated  to  con- 
stant weight  in  a  platinum  dish  in  the  water-oven  or  on  a 
water-bath. 

Ash. — A.  W.  Smith  makes  the  following  suggestions  for 
its  examination  and  determination  :  10  grams  of  the  sample 
should  be  evaporated  and  ashed  by  small  portions  (not  more 
than  10  c.c.)  at  not  above  a  low  red  heat.  The  residue  is 
dissolved  and  tested  qualitatively  by  the  flame-test  and  for 
chlorids  and  sulfates.  Unless  the  latter  are  present  in  excess 
of  the  amount  usually  found  in  pure  samples,  they  need  not 
be  determined  quantitatively.  For  alkalinity  of  the  ash  and 
proportion  of  phosphates,  25  grams  of  the  sample  are  dried 
and  burned,  the  ash  extracted  repeatedly  with  hot  water,  and 
the  aqueous  solution  titrated  with  standard  acid,  using  methyl- 
orange  as  indicator.  The  undissolved  residue  is  treated  with 
nitric  acid,  the  solution  partially  neutralized,  and  the  phos- 
phates in  each  solution  determined. 

Nitrogen. — 50  c.c.  are  evaporated  to  small  bulk  and  treated 
by  the  Kjeldahl-Gunning  method. 

Mineral  Acid. — If  the  ash  be  alkaline,  no  mineral  acid  can 
have  been  present  except  nitric  acid  ;  but  if  neutral,  A.  Ash- 
by's  test  should  be  applied.  A  drop  of  solution  of  logwood 
extract  in  water  (0.5  gram  to  100  c.c.)  is  dried  on  a  porcelain 
plate,  a  drop  of  the  vinegar  added,  and  again  dried.  The 


VINEGAR  289 

residue  from  pure  vinegar  will  be  yellow,  but  will  be  red  if  min- 
eral acid  be  present.  If  the  proportion  of  acid  be  small,  the 
red  color  is  destroyed  by  the  addition  of  water,  but  is  restored 
on  evaporation,  except  in  the  case  of  nitric  acid,  which  does 
not  appear  to  be  used  for  adulteration. 

The  amoupt  of  free  mineral  acid  is  determined  by  O.  Heh- 
ner's  method  as  follows  :  50  c.c.  of  the  sample  are  mixed 
with  a  measured  amount  of  decinormal  alkali,  preferably  less 
than  sufficient  to  neutralize  all  the  acid,  but  rather  more  than 
sufficient  to  neutralize  the  mineral  and  fixed  organic  acids 
present.  The  mixture  is  evaporated  to  dryness,  ashed  at  a 
low  red  heat,  and  titrated  with  standard  acid.  In  the  absence 
of  mineral  acid,  the  ash  will  have  an  alkalinity  equal  to  the 
standard  alkali  added.  Any  deficiency  in  alkalinity  will  be 
due  to  the  presence  of  mineral  acid. 

Vinegar  containing  sulfuric  acid  usually  leaves  a  charred 
residue  on  evaporation  in  the  water-bath.  For  samples  con- 
taining but  little  organic  solids  the  test  may  be  made  applicable 
by  adding  a  little  sucrose.  Sulfuric  acid  as  distinguished  from 
sulfate  may  be  determined  by  A.  H.  Allen's  method  as  follows  : 
100  c.c.  of  the  vinegar  are  evaporated  to  10  c.c.,  and  to  the 
cold  concentrated  liquid  50  c.c.  of  alcohol  are  added.  Sulfates 
are  precipitated,  but  sulfuric  acid  remains  in  solution.  The 
filtered  liquid  is  diluted,  the  alcohol  boiled  off,  and  the  sul- 
furic acid  determined  by  precipitation  with  barium  chlorid. 
In  vinegar  free  from  chlorids  this  process  gives  results  in 
accordance  with  Hehner's  process,  but  when  chlorids  are 
present  the  mineral  acid  found  is  deficient  by  the  amount 
required  to  decompose  the  chlorids.  This  difficulty  may  be 
overcome  by  treating  the  sample  with  excess  of  solution  of 
silver  sulfate  before  evaporation,  by  which  any  free  hydro- 
chloric acid  will  also  be  estimated  as  sulfuric  acid. 

Caramel  may  be  detected  by  the  method  given  on  page  1 30. 

Potassium  acid  tartrate,  which  occurs  in  true  wine  vinegar, 
25 


290  FOOD    ANALYSIS 

may  be  detected  by  dissolving  the  solid  residue  in  a  little 
water,  adding  alcohol  and  stirring  the  mixture  with  a  glass 
rod  ;  the  tartrate  will  be  deposited  in  crystals  along  the  lines 
touched  by  the  rods. 

Poisonous  metals  may  be  encountered,  especially  in  vinegar 
containing  free  mineral  acid.  Arsenic  may  be  detected  by 
Reinsch's  test  (p.  71).  Lead,  copper,  tin,  and  zinc  may  be 
tested  for  directly  in  light-colored  vinegars,  but  in  most  cases 
it  will  be  necessary  to  examine  the  ash  in  accordance  with  the 
methods  given  on  page  69. 


SPICES 

Spices,  being  generally  sold  for  household  uses  in  finely 
powdered  form,  are  very  liable  to  adulteration,  and  much 
attention  has  been  given  the  nature  and  detection  of  the 
adulterants.  Microscopic  and  chemical  methods  are  needed, 
and  successful  application  of  these  tests  to  samples  of  un- 
known origin  can  only  be  safely  made  after  considerable 
experience  with  materials  of  known  purity.  Standards  should 
be  prepared  from  the  un ground  material  properly  identified. 
The  mounting,  dissolving,  and  staining  agents  described  on 
page  35  should  be  employed.  In  some  cases  adulteration 
may  be  identified  by  form  of  starch  granules,  but  this  often 
requires  great  care  and  patience. 

More  attention  has  been  given  to  the  chemistry  and 
microscopy  of  pepper,  on  account  of  use  of  this  spice  and  its 
frequent  adulteration.  Cream  of  tartar  is  classified  as  a 
spice  in  the  grocery  trade. 


PEPPER 

Pepper  is   the  fruit  of  the  Piper  nigrum  L.,  of  the  order 
Piperacece.     Black  pepper  is  the   unripe  fruit,   dried  in  the 


PEPPER  291 

sun  ;  white  pepper  is  obtained  by  soaking  the  ripe  fruit  in 
water  and  removing  the  husks  by  friction. 

Pepper  contains  alkaloid,  piperin,  an  acrid  resin,  a  volatile 
oil,  starch,  a  small  amount  of  nitrates,  and  the  usual  plant 
constituents. 

Piperin  exists  in  a  number  of  plants  belonging  to  the  Piper- 
acece.  The  proportion  present  in  pepper  ranges  between  4 
and  8  per  cent.  Piperin  forms  colorless  four-sided  monoclinic 
prisms,  melting  at  128°  and  decomposing  at  a  slightly  higher 
temperature.  It  is  insoluble  in  cold  and  but  slightly  soluble 
in  hot  water,  dissolves  in  alcohol,  forming  a  neutral  solution 
of  pungent  taste,  is  freely  soluble  in  chloroform,  benzene,  and 
petroleum  spirit,  but  less  so  in  ether.  It  is  extracted  even 
from  acid  solutions  by  chloroform.  Boiled  with  strong  alkali, 
it  is  converted  into  piperidin  and  a  piperate. 

'Piperidin  is  a  colorless  liquid  with  an  odor  recalling  both 
ammonium  hydroxid  and  pepper.  It  boils  at  1 06°,  is  strongly 
basic,  and  may  be  estimated  by  titration  with  standard  acid, 
using  methyl-orange  as  indicator.  Small  proportions  are 
found  in  pepper.  According  to  Johnstone,  black  pepper  con- 
tains from  0.39  to  0.77  per  cent,  and  white  pepper  from  0.21 
to  0.42  per  cent. 

The  resin  of  pepper  is  dark  green  and  has  a  hot  pungent 
taste.  It  is  soluble  in  alcohol,  ether,  and  sodium  hydroxid 
solution,  and  also  in  water  in  the  presence  of  the  other  con- 
stituents of  pepper. 

The  volatile  oil  of  pepper  is  a  terpene  having  a  boiling- 
point  of  167°-! 70°.  It  has  the  smell  of  pepper,  but  not  its 
pungency.  It  is  usually  present  to  the  extent  of  about  I  per 
cent. 

Starch. — Pepper-starch  is  in  minute  granules,  not  more 
than  0.005  mm-  m  diameter,  round  or  polygonal,  and  often 
in  clusters.  Under  a  high  power  they  show  a  central  nucleus 
or  vesicle. 


2Q2 


FOOD    ANALYSIS 


The  microscopic  appearance  of  ground  pepper  is  shown  in 
the  annexed  cut,  from  a  drawing  by  Moeller.35 

Adulteration  of  Pepper. — The  following  are  some  of  the 
adulterants  which  may  be  looked  for  in  pepper :  Pepper 


am 


ep 


ist--- 


am 


as 


FIG.  49. 

A,  Starch  granules  (X  600)  ;  atn,  cell  containing  starch  ;  /,  parenchyma  with 
resin  ;  bf,  bast  fibers ;  bp,  bast  parenchyma ;  sp,  spiral  vessels ;  ep,  epider- 
mis ;  as/,  stony  parenchyma ;  as  and  zV,  setd  membrane  in  two  layers ; 
ist,  inner  stone-cell  layer  with  horseshoe-shaped  cells.  The  structures  ist, 
as,  and  is  are  more  characteristic,  especially  the  two  latter,  consisting  of  a 
light  and  a  dark  layer.  All  (except  A,  as  above)  X  Io^>- 

husks,  long-pepper,  wheat,  buckwheat,  cayenne  pepper,  mus- 
tard husks,  ground  olive  stones  (poivrette  or  pepperette), 
almond  and  coconut  shells  (often  roasted  or  charred),  Egyp- 
tian corn,  spent  ginger,  and  coriander  seed.  Of  mineral 


PEPPER  293 

additions,  sand,  clay,  brick  dust,  chalk,  barium  sulfate,  and 
lead  chromate  are  known  to  have  been  used. 

In  the  examination  of  pepper,  considerable  reliance  must 
be  placed  upon  the  microscopic  characters.  Numerous  chemi- 
cal examinations  have  been  made,  but  the  results  in  many 
cases  have  been  conflicting,  and  the  uncertainty  has  been 
increased  by  the  fact  that,  until  quite  recently,  hardly  any  two 
workers  have  employed  the  same  methods. 

The  chemical  examination  should  be  directed  especially  to 
the  determination  of  moisture,  ash,  ether-extract,  and  crude 
fiber.  The  alcohol  and  water-extract  have  been  shown  to  be 
valueless  in  this  connection. 

Moisture. — This  is  determined  as  on  page  38.  The  drying 
in  hydrogen  may  require  to  be  continued  8  hours  before 
constant  weight  is  attained.  The  loss  in  weight  will  represent 
a  small  amount  of  volatile  oil  as  well  as  water. 

Ether-extract. — This  will  contain  piperin,  resin,  and  some 
volatile  oil,  and  for  the  purpose  of  detecting  adulteration  is 
more  convenient  and  satisfactory  than  the  determination  ot 
piperin  alone.  If  desired,  the  piperin  may  be  determined  as 
follows  :  The  mixture  of  piperin  and  resin  obtained  by  extrac- 
tion is  treated  with  sodium  hydroxid,  by  which  the  resin  is 
dissolved  ;  the  residue  is  dissolved  in  alcohol,  the  solution 
filtered,  evaporated,  and  the  residue  (piperin)  weighed.  An- 
other method  is  to  mix  a  weighed  portion  of  the  powdered 
pepper  with  slaked  lime  and  water,  dry  at  100°,  and  thoroughly 
extract  with  ether.  The  residue  left  on  the  evaporation  of 
the  ether  is  purified  by  solution  in  alcohol,  filtration,  and 
crystallization. 

The  proportion  of  ether-extract  is  usually  not  less  than  7  per 
cent.,  but  may  fall  below  this  figure  even  in  pure  peppers. 
(See  results  page  296.) 

Crude  Fiber. — This  should  be  determined  on  the  ether- 
extracted  material  as  described  on  page  46.  C.  Richardson's 


294  FOOD    ANALYSIS 

figures  and  those  of  Winton  in  the  following  table  were 
obtained  in  this  way.  Those  of  Stokes  were  made  without 
previous  exhaustion  with  ether.  Heisch  reported  "  cellulose," 
but  the  method  of  determination  is  not  stated.  Using  the 
method  as  recommended  by  the  A.  O.  A.  C.,  it  is  probable 
that  pepper  will  not  yield  more  than  16  per  cent,  of  fiber. 

ANALYST, C.  RICHARDSON.        WINTON.  STOKES.  HEISCH. 


Black  pepper, 
White  pepper, 

.  80  to  II.  o 

.    .  4.1  to    8.0 

8.57  to  15.41 
3.32  to    4.16 
7.38 

21.  0  to  26.3 

12.7  to  13.8 
20  o  to  22.3 

11.5  to  27.8 

3.410   6.7 

1.  14  to  12.  9 

Pepper    shells 
dust,  .    .    . 
Olive  stones, 

or 

/    O 
22.8 

62.2  to  64.2 

61.9  to  68.8 

Ash. — In  unadulterated  black  pepper  the  proportion  of  ash 
rarely  exceeds  5  per  cent.;  over  65  per  cent,  may  be  taken  as 
positive  evidence  of  adulteration.  The  ash  of  white  pepper 
should  not  exceed  3  per  cent.  If  long  pepper  be  present,  the 
ash  is  apt  to  be  high,  for  the  reason  given  below.  Stock  has 
published  the  following  determinations  in  genuine  peppers  : 

TELLICHERRY.  SIAM.  LAMPONG.  PENANG. 

Ash, 1.05  1.45  2.20  2.75 

Fiber, 4.86  4.43  4.90  5.06 

Calc.  carb.  in  pepper,  .0.58  0.62  0.81  1.67 

"         "      "ash,    .    .55.20  42.70  36.80  60.70 

TELLICHERRY  PEPPER.                 UNHULLED.  HULLED. 

Total  ash, 4.02  1.64 

Fiber, 10.40  6.80 

Ratio  of  calcium  (as  carbonate)  to  ash,     .  27.30  62.00 

It  is  thus  seen  that  calcium  compounds  are  more  abundant 
in  pepper.  Excess  of  hulls  results  in  a  lowering  of  this  ratio, 
but  the  proportion  may  be  altered  in  samples  that  have  been 
bleached  or  faced  with  mineral  matter.  Stock  considers  that 
in  pure  pepper  the  proportion  of  calcium  carbonate  to  total 
ash  is  never  greater  than  60  per  cent. 

It  is  advisable  to  shake  up  a  portion  of  the  pepper-sample 


PEPPER  295 

with  chloroform  in  a  tapped  separator.  The  heavier  mineral 
additions  will  sink,  along  with  more  or  less  husk,  and  may  be 
removed  by  means  of  the  tap  and  examined  with  the  micro- 
scope and  chemically.  In  this  way  it  may  be  possible  to 
distinguish  between  added  mineral  matter  and  that  naturally 
present. 

From  the  results  of  examination  of  samples,  either  known 
to  be  pure,  or  in  which  the  microscope  failed  to  show  any 
structure  except  that  natural  to  pepper,  A.  L.  Winton  has 
proposed  the  following  limits  of  composition  for  black 
pepper  : 

Ether-extract  dried  at  100°,     .    .  not  less    than    6.5  per  cent. 

Fiber, not  more  than  16.0       " 

Ash, "  "       6.5       " 

Sand,      "  "       2.0       " 

The  methods  of  the  A.  O.  A.  C.  were  used  in  the  examina- 
tions. The  same  observer  has  called  attention  to  the  fact 
that  in  the  ether-extract  of  pure  pepper  the  piperin  invariably 
crystallizes  out  from  the  resin  on  cooling,  but  that  when 
pepper  is  adulterated  with  material  containing  fat  or  oil,  the 
latter  may  conceal  the  crystals  or  prevent  their  formation. 
Absence  of  piperin  crystals  is  regarded  as  positive  evidence  of 
adulteration.  If  the  fat  or  oil  introduced  by  the  adulterant 
increases  the  weight  of  the  extract  to  the  amount  which  is 
found  in  pure  pepper,  a  determination  of  the  nitrogen  in  the 
extract  from  10  grams  will  often  disclose  its  real  nature.  A 
sample  of  pure  white  pepper  gave  an  extract  containing  3.25 
per  cent,  of  nitrogen,  and  that  from  pure  black  pepper  2.64 
per  cent.  In  adulterated  samples  the  proportion  will  often 
fall  considerably  below  2  per  cent.  A  sample  of  pepper  shells 
(pepper  dust)  examined  by  Winton  gave  the  following  results  : 
Water,  8.36  ;  ether-extract,  6.98  ;  fiber,  22.  88  ;  total  ash,  9. 19  ; 
sand,  2.28. 

According  to  the  figures  given  by  the  A.  O.  A.  C.,  the 


296  FOOD    ANALYSIS 

following  limits  of  composition  will  probably  include  all  good 
pepper.  All  samples  having  over  5  per  cent,  of  ash  or  over 
1 1  per  cent,  of  fiber  are  regarded  with  suspicion  : 

BLACK  PEPPER.  WHITE  PEPPER. 

Moisture, 8  to  12  12  to  15 

Ash,          2.75106.5  0.8  to  2.9 

Starch  (direct  inversion  by  hydro- 
chloric acid), 32  to  38  40  to  53 

Fiber, 9  to  16  4  to  8 

Albuminoids, 7  to  12  8  to  12 

Non-volatile  ether  extract,  not  less 

than, 6.5  7  to  8 

Starch. — Many  determinations  have  been  made,  but  the 
methods  used  have  been  faulty  and  the  indications  often  un- 
satisfactory. C.  Heisch  boiled  the  pepper  for  three  hours 
with  10  per  cent,  hydrochloric  acid  and  measured  the  optic 
activity  of  the  resulting  liquid.  The  gum  and  other  soluble 
matters  were  found  to  cause  a  rotation  equivalent  to  about  I 
per  cent,  of  starch.  Lenz  extracted  the  pepper  with  water, 
boiled  the  residue  with  hydrochloric  acid,  and  determined  the 
reducing  sugar.  All  the  samples  of  pepper  examined  gave 
a  reducing  sugar  equivalent  of  over  50  per  cent.,  while  the 
adulterants,  except  those  containing  starch,  gave  under  30  per 
cent.  Rottger,  however,  found  Lampong  pepper  to  give  a 
"  reducing-sugar  equivalent  "  of  only  41.7  per  cent.  Richard- 
son found  the  starch  in  5  samples  of  black  pepper  to  vary 
between  34 and  38  per  cent,  of  the  dry  ash-free  material.  In 
two  samples  of  white  pepper  the  figures  were  about  40  and  43 
per  cent,  respectively. 

Substances  other  than  starch  are  converted  into  sugar  by 
the  above  processes,  and  more  satisfactory  conclusions  might 
be  drawn  from  an  accurate  determination  of  the  starch  by  the 
diastase  method,  as  described  on  page  97. 

Total  Nitrogen. — This  is  determined  by  the  Kjeldahl-Gun- 
ning  method.  Richardson  found  1.83  and  1.90  per  cent,  of 


PEPPER  297 

nitrogen  in   two   samples   of  white  pepper  and  from  1.57  to 
2.10  per  cent,  in  five  samples  of  black  pepper. 

Busse  considers  that  the  true  value  of  a  pepper  is  best 
shown  by  a  quantitative  estimation  of  the  brown  coloring- 
matter,  which  is  only  found  in  the  husk.  He  proposes  the 
following  method  :  5  grams  of  the  sifted  and  dried  pepper  are 
treated  with  boiling  absolute  alcohol.  The  extract,  after 
being  freed  from  alcohol  in  the  drying  oven,  is  ground  up 
with  a  little  water  in  a  basin,  and  then  washed  into  a  flask  with 
50  to  60  c.c.  of  boiling  water.  25  c.c.  of  a  10  per  cent,  solu- 
tion of  sodium  hydroxid  are  added  and  the  flask  warmed  on 
the  water-bath  for  five  hours,  with  frequent  shaking.  Con- 
centrated acetic  acid  is  added  until  the  liquid  is  only  feebly 
alkaline,  then  250  c.c.  of  water,  and  the  flask  well  shaken. 
After  12  hours  the  liquid  is  filtered  with  the  aid  of  a  filter 
pump.  To  50  c.c.  of  the  filtrate  concentrated  acetic  acid  is 
added  to  acid  reaction  and  20  c.c.  of  a  10  per  cent,  solution 
of  lead  acetate  in  dilute  acetic  acid.  After  mixing,  the  liquid 
is  diluted  to  100  c.c.  with  water,  well  shaken,  and  filtered. 
10  c.c.  of  the  filtrate  are  decomposed  with  5  c.c.  of  sulfuric 
acid  (1:3)  and  30  c.c.  of  alcohol,  the  precipitate  filtered  after 
some  time,  washed  with  alcohol,  the  lead  sulfate  ignited  in 
the  usual  manner,  and  the  amount  of  lead  calculated.  The 
amount  of  lead  in  grams  which  has  been  obtained  by  the  pro- 
cess from  I  gram  of  the  dried  pepper  is  designated  as  the 
"  lead  number."  The  following  figures  are  given  : 

LEAD  NUMBER. 

White  pepper, 0.006  to  0.027 

Black  pepper,    . 0.054  to  0.075 

Husks 0.129100.157 

Pepper  dust, 0.109100.122 

Ground  olive -stones,  termed  "  poivrette  "  and  "  pepperette," 
have   been    much    used  to  adulterate  pepper.     J.    Campbell 
Brown,  who  first  called  attention  to  this  use,  has  given  the 
results  of  analysis  of  samples  : 
26 


298 


FOOD    ANALYSIS 


ASH. 


White  pepperette, 1.33 

Black  pepperette, 2.47 

Ground  olive-stones, i.6l 

Ground  almond-shells, 2.05 


FIBER. 
48.48 
47.69 

45-3« 
51.68 


None  of  the  samples  contained  starch. 

Poivrette  is  a  pale  buff  or  cream-colored  powder,   which 
cannot  be  distinguished  from  the  materials  of  genuine  pepper 


a 


FIG.  50. 

a,  Cells  associated  with  the  vascular  bundles,  also  some  stone-cells  ;  z,  inner  layer 
of  hard  cells,  with  endothelium  en  ;  p,  cells  from  the  fleshy  portion  of  the 
fruit;  ep,  epidermis  of  the  seed  wall,  with  brown  parenchyma  showing 
through  it ;  ea,  exterior  layer  of  the  endosperm.  Some  spiral  vessels  are  also 
shown.  X  I^°. 

by  simple  inspection.  The  particles  are,  however,  tough  and 
hard,  and  may  be  sometimes  detected  by  crushing  the  sample 
between  the  teeth.  Under  the  microscope  the  powder  shows 
dense  ligneous  cells,  some  entire,  with  linear  air-spaces,  others 
torn  and  indistinct.  Figure  50  shows  some  structures  of  olive 
seed  and  figure  5  I  some  structures  of  nut-shells.  Both  are 
from  J.  Moeller's  work.36 


PEPPER 


299 


By  treatment  with  dilute  sodium  hydroxid  solution  and 
washing  by  decantation  poivrette  will  appear  yellow  and 
pepper  husk  dark.  Although  poivrette  contains  no  starch,  it 
yields  a  reducing  substance  on  boiling  with  hydrochloric  acid. 

Bleached  pepper  husks  are  distinguished  from  poivrette  by 
the  microscopic  appearance.  An  incomplete  separation  of 
poivrette  may  be  effected  by  shaking  the  sample  in  a  mixture 
of  equal  parts  of  glycerol  and  water,  in  which  poivrette  sinks 
more  rapidly. 

Several  color  tests  have  been  proposed.  Gillet  advises 
the  use  of  a  7  per  cent,  alcoholic  solution  of  iodin,  which 
stains  pepper  brown  and  poiv- 
rette bright  yellow.  Chevreau 
uses  a  solution  of  anilin  in  three 
parts  of  acetic  acid.  Pure  pep- 
per is  almost  unaffected,  but 
poivrette  becomes  bright  yel- 
low, and  under  the  microscope 
the  stone  cells  exhibit  a  pure 
gamboge  yellow.  Pabst  uses  a 
solution  of  dimethyl- 1 -4-di- 
amidobenzene,  prepared  as  fol- 
lows :  i  gram  of  commercial  di- 
methylanilin  is  mixed  in  a  por- 
celain dish  with  2  grams  of  strong  pure  hydrochloric  acid,  10 
grams  of  broken  ice  are  added,  and,  little  by  little,  with  con- 
stant stirring,  a  solution  of  0.7  gram  of  sodium  nitrate  in  10  c.c. 
of  water.  After  half  an  hour  3  to  4  grams  of  hydrochloric 
acid  and  2  grams  of  tin-foil  are  added.  The  reduction  is  allowed 
to  go  on  for  an  hour,  when  the  tin  in  solution  is  precipitated 
by  means  of  zinc.  The  decanted  and  filtered  liquid  is  treated 
with  a  slight  excess  of  sodium  carbonate  and  the  precipitate 
thus  produced  redissolved  by  the  addition  of  acetic  acid.  I 
gram  of  sodium  acid  sulfite  is  added  and  the  liquid  diluted 


FIG.  51. 

Exterior  layer;    m,  intermediate 
layer ;  i,  inner  layer. 


3OO  FOOD    ANALYSIS 

to  200  c.c.  In  testing  pepper,  2  c.c.  of  the  solution  are 
placed  in  a  shallow  dish  and  a  pinch  of  the  pepper  sprinkled 
into  it.  In  a  few  minutes  the  particles  of  olive  stones  become 
a  brilliant  carmine,  while  the  grains  of  pepper  remain  unal- 
tered or  become  only  faintly  pink.  If  some  water  be  now 
added,  the  heavy  particles  of  olive  stones  fall  to  the  bottom 
and  are  detected  with  ease.  Ground  nut-shells  are  colored  in 
the  same  way. 

The  phloroglucol-hydrochloric  acid  solution  (page  35)  pro- 
duces with  olive  stones  and  nut-shells  a  deep  crimson  stain 
which  is  very  characteristic.  The  action  is  obtained  promptly 
on  moistening  the  sample  with  a  few  drops  of  the  reagent. 
Under  a  magnifying  power  of  about  200  diameters  the  stained 
stone-cells  are  clearly  seen. 

Dhoura  Corn. — This  is  a  variety  of  sorghum,  known  in 
England  as  Turkish  millet  and  in  America  as  Egyptian  corn. 
J.  Campbell  Brown  has  called  attention  to  its  use  as  an 
adulterant  for  pepper,  and  gives  the  following  analyses  and 
description.  The  samples  examined  contained  1 1  per  cent, 
of  moisture,  and  the  figures  given  are  percentages  of  the  dry 
material : 

Ash, 1.31  1.69 

Starch, 73.20  73.20 

Cellulose 2.56  4.19 

Ether-extract, li.io  7.30 

Nitrogen, 1.82  1.78 

The  material  designated  "cellulose"  is  probably  crude 
fiber,  obtained  by  using  stronger  solutions  than  directed  in 
the  A.  O.  A.  C.  method.  The  grain  is  roundish,  oval,  or  some- 
what flattened,  2  to  5  mm.  in  diameter.  The  body  is  white  and 
consists  mainly  of  roundish  starch  granules,  ranging  from 
1.5  to  2.5  microns  in  diameter,  showing  a  cross  under  polar- 
ized light,  and  larger  granules,  ranging  from  12.5  to  32.5 


PEPPER  3OI 

microns  in  diameter,  showing  almost  no  cross.  Some  of 
the  smaller  granules  have  a  star-like  central  hilum. 

Coriander  Seed. — Hanausek  has  called  attention  to  the 
adulteration  of  pepper  with  ground  coriander  seed.  The 
following  peculiarities  were  observed  under  the  microscope  : 
(a)  bundles  of  corrugated  bent  fibrous  cells ;  (b)  coarse 
parenchyma  overlaid  with  narrow  cells  of  a  yellow  color,  with 
parallel  walls  ;  (c]  colorless  cellular  parenchyma  firm  in  the 
walls  and  inclosing  numerous  crystalline  rosettes  and  granules. 
The  last  two  peculiarities  were  recognized  as  characteristic  of 
a  fruit  of  the  order  Umbelliferce,  the  bundles  of  fibers,  as  well 
as  the  absence  of  vittae  (oil  cavities),  pointing  to  coriander. 

Cayenne  pepper  is  often  added  to  adulterated  pepper  to 
restore  pungency.  It  may  be  detected  by  the  characteristic 
irritating  vapor  produced  on  heating  some  of  the  separated 
red  particles.  An  alcoholic  or  ethereal  solution  also  gives  off 
such  vapors. 

LONG    PEPPER 

Long  pepper  is  the  fruit  of  at  least  two  species,  formerly 
included  under  the  genus  Piper  L.  (Piperacece),  now  included 
under  the  genus  Cliavica  Miq.  It  consists  of  long,  nearly 
cylindrical  spikes,  covered  with  closely  packed  coalesced 
fruit,  which  are  picked  unripe.  The  Chavica  officinarum, 
from  Java,  consists  of  spikes  about  4  to  6  cm.  in  length. 
The  spikes  of  the  Chavica  Roxburghii  are  about  half  as  long. 
The  latter  is  the  more  common  form. 

Long  pepper  usually  contains  a  considerable  proportion  of 
extraneous  matter  (clay  and  soil)  embedded  in  the  crevices 
and  irregularities  of  the  fruit.  The  outer  husk  and  central 
woody  stem  are  not  readily  removed,  as  in  the  case  of  black 
pepper,  so  that  the  proportion  of  woody  fiber  is  larger  than 
in  ground  black  pepper  of  the  same  shade,  but  not  so  high  as 
in  most  husky  black  pepper.  Long  pepper  contains  less 
piperin  than  most  black  pepper,  and  has  a  disagreeable  odor 


STARCH  AND 
MATTER  CON- 

INSOL 

VERTIBLE 

ETHER- 

HC1. 

INTO  SUGAR. 

FIBER. 

EXTRACT. 

NITROGEN. 

ANALYST. 

1.2 

44.04 

15-7 

5-5 

2.1 

J.  C.  Brown 

I.I 

49-34 

10.5 

4-9 

2.0 

« 

i-S 

4461 

10.7 

8.6 

2.3 

<  < 

.    . 

7.28 

7.24 

A.  L.  Winton 

3O2  FOOD    ANALYSIS 

and  flavor ;  in  the  ground  state,  it  is  not  a  recognized  article 
of  commerce.  It  is  used  whole  in  pickles  and  has  been 
employed  to  adulterate  ground  black  and  white  pepper.  The 
following  are  some  results  of  analysis  of  long  pepper  : 

TOTAL 
ASH. 

8.91 
8.98 
9.61 
8.10 

Winton's  figures  were  obtained  by  the  A.  O.  A.  C.  methods. 

According  to  J.  Campbell  Brown,  long  pepper  may  be 
detected  in  ground  pepper  by  the  following  characters  :  The 
presence  of  any  considerable  quantity  of  long  pepper  will 
impart  to  the  ground  material  its  peculiar  slaty  color ;  but 
this  is  made  much  lighter  by  the  practice  of  sifting  out  much 
of  the  darker  or  husky  portions  of  the  long  pepper  before 
mixing.  Bleaching  is  also  resorted  to.  The  odor  of  the 
mixture  when  warmed  is  unmistakable,  even  if  the  quantity 
is  comparatively  moderate.  The  ether-  or  alcohol-extract 
also,  if  the  solvent  has  been  evaporated  at  a  low  temperature, 
yields  the  characteristic  odor  when  warmed. 

Long  pepper  often  introduces  a  considerable  amount  of 
mineral  matter,  especially  sand  and  other  material  insoluble 
in  acid.  This  fact  is  important  in  examining  white  peppers,  in 
which  the  proportion  of  ash  is  low.  Long  pepper,  even  if  the 
husk  particles  have  been  sifted  out,  will  still  introduce  some 
sand,  as  well  as  spent  bleach,  if  an  attempt  has  been  made  to 
bleach  it. 

The  woody  matter  in  ground  long-pepper  is  always  con- 
siderable. If  the  sample  be  spread  out  in  a  smooth  thin  layer 
on  paper  by  means  of  an  ivory  paper-knife,  pieces  of  fluffy 
woody  fiber  will  be  detected,  especially  if  the  smooth  thin 
layer  be  tapped  from  below.  These  pieces  come  from  the 


CAYENNE    PEPPER  303 

central  part  of  the  indurated  catkin,  which  cannot  be  com- 
pletely ground  fine,  and  are  very  characteristic. 

Some  of  the  starch  granules  of  long  pepper  are  of  larger 
size  (0.005  mm.)  than  those  of  ordinary  pepper,  which  are 
but  slightly  smaller  than  those  of  rice. 

According  to  Stokes,  long  pepper  may  be  detected  by 
placing,  a  small  portion  on  a  microscope  slide,  adding  a  drop 
of  glycerol,  and  examining  under  a  power  of  about  50  diam- 
eters and  crossed  Nicols.  If  ordinary  pepper  only  be  pres- 
ent, the  field  will  remain  dark,  but  long  pepper  presents  a 
luminous  white  appearance.  The  same  is  true  of  particles  of 
rice.  By  treating  the  finely  powdered  material  for  24  hours 
with  chloral  solution,  it  is  rendered  more  transparent,  and 
more  satisfactory  examination  may  be  made.  Rimmington 
recommends  shaking  the  material  several  times,  first  with 
alcohol  and  then  with  water  in  a  test-tube,  and  allowing  to 
subside.  Several  strata  are  usually  formed,  the  uppermost  of 
which  should  be  removed  by  means  of  a  pipet  and  examined 
with  a  power  of  250  diameters.  Every  particle  will  be  seen 
clear  and  well  defined  and  foreign  bodies  easily  recognized. 


CAYENNE  PEPPER 

Cayenne  pepper  is  the  ground  pods  of  several  species  of 
Capsicum,  usually  C.  annuum  L.  or  C.  fastigiatum  Blum.  The 
latter  is  official  in  the  United  States  and  British  pharma- 
copeias. It  is  known  in  commerce  as  African  or  bird  pepper, 
and  in  Great  Britain  as  Guinea  pepper  and  as  chillies.  The- 
pods  are  bright  scarlet  and  from  12  to  18  mm.  in  length. 
Those  of  C.  annuum  are  much  larger,  5  to  10  cm.,  yellowish 
or  red,  and,  when  dry,  brownish ;  in  other  respects  they 
resemble  those  of  C .  fastigiatum. 

Cayenne  pepper  is  a  brick-red  powder  of  intensely  pungent 
taste  and  characteristic  odor.  When  heated,  an  acrid,  irritat- 


304  FOOD    ANALYSIS 

ing  vapor  is  given  off,  the  production  of  which  maybe  utilized 
as  a  test  for  the  pepper,  even  on  a  minute  quantity  of  the 
material.  This  is  due  to  a  crystalline  body,  "  capsaicin." 
It  melts  at  59°  and  volatilizes  at  115°.  It  may  be  obtained 
by  extracting  the  pepper  with  petroleum  spirit,  evaporating, 
and  treating  the  dry  extract  with  a  dilute  solution  of  potassium 
hydroxid.  On  saturating  the  liquid  with  carbon  dioxid  the 
capsaicin  is  precipitated  in  small  crystals,  readily  soluble  in 
alcohol,  ether,  amyl  alcohol,  and  fixed  oils,  but  less  so  in 
petroleum  spirit  and  carbon  disulfid.  Capsaicin  is  more 
abundant  in  the  pods  than  in  the  seeds,  in  which  it  exists 
dissolved  in  the  fixed  oil.  It  was  discovered  by  Thresh,  who 
found  also  a  small  quantity  of  an  alkaloid  resembling  conin. 
The  coloring-matter  of  cayenne  pepper  is  but  slightly  soluble 
in  alcohol,  but  dissolves  readily  in  oils,  carbon  disulfid, 
petroleum  spirit,  ether,  and  chloroform.  The  odor  is  due,  at 
least  in  part,  to  the  presence  of  a  minute  quantity  of  volatile 
oil. 

Cayenne  pepper  contains  no  starch. 
The  following  are  some  published  analyses  : 
Fruit  of  Capsicum  annuum,  grown  in  Hungary  (C.  Richard- 
son) : 

WHOLE 
SEED.  POD.  FRUIT. 

Water  at  1 00°, 8.12  14-75  I][-94 

Albuminoids,       18.31  10.69  13.88 

Ether-extract, 28.54  5.48  15.26 

Nitrogen-free  matter  by  difference,  .  24.33  3^-73  32.63 

Crude  fi  er, 17.50  23.73  21.09 

Ash, •   .    .     3.20  6.62  5.20 

Nitrogen, 2.93  1.71  2.22 

Average  of  several  analyses  by  Blyth  : 

Water-extract,       32.10 

Alcohol-extract, 25.79 

Benzene-extract,   .    .    .    .- 20.00 

Ether-extract, 10.73 

Nitrogen, 2.04 

Ash, 5.69 


GINGER  305 

Two  analyses  by  C.  Richardson  : 

ETHER-  ALBUM-    NITRO- 

WATER.      ASH.        EXTRACT.      FIBER.       INOIDS.       GEN. 

Zanzibar, 2.35         9.06         26.99         16.88         13. 13         2.10 

Crosse  and  Blackwell,    .    .5.74         5.24         17-9°         18. 10         11.20         1.79 

Adulteration. — The  adulterant  most  commonly  added  to 
cayenne  pepper  is  rice  flour  or  similar  material.  Brick  dust 
is  also  used.  -  A.  H.  Allen  found  iron  oxid,  salt,  and  red 
lead.  Starch-containing  materials  are  readily  detected  by  the 
microscope  or  by  the  iodin  test. 

Results  obtained  at  the  Connecticut  Agricultural  Experi- 
ment Station  indicate  that  pure  cayenne  pepper  will  contain 
not  less  than  16  per  cent,  of  non-volatile  ether-extract  and 
between  4.5  and  8  per  cent,  of  ash. 

The  determinations  of  extract,  ash,  nitrogen,  and  moisture 
are  made  by  the  methods  elsewhere  given.  Barium  com- 
pounds have  been  found  in  some  samples,  and  it  has  been  al- 
leged that  they  are  normal,  but  this  seems  to  be  a  mistake. 

An  artificial  red,  containing  barium,  is  sometimes  used  to 
color  inferior  samples,  and  possibly  barium  sulfate  has  been 
added  as  a  make-weight. 

The  following  data  have  been  furnished  as  the  range  of 
composition  in  cayenne  pepper.  An  ether-extract  of  less 
than  1 8  per  cent,  is  suspicious  : 

Moisture, 2      to  10     per  cent. 

Ash, 5      to  10 

Fiber, 16     to  18 

Nitrogen, 1.7  to    2.2 

Ether-extract, 16     to  30 

Alcohol-extract, 25      to  45 

GINGER 

Ginger  is  the  rhizome  of  the  Zingiber  officinale  Roscoe,  of 
the  order  Zingiberacece.  It  exists  in  commerce  in  two 
forms,  either  with  the  outer  integument  present,  called 


306  FOOD    ANALYSIS 

"coated  ginger,"  or  removed  by  scraping,  as  in  "  uncoated  " 
or  "  scraped  ginger."  Scraped  ginger  is  sometimes  known 
as  white  ginger,  and  the  same  name  is  applied  to  samples  that 
have  been  bleached  either  with  sulfurous  acid  or  hyposulfites. 
It  is  also  sometimes  coated  with  lime  or  gypsum.  Jamaica 
ginger  is  preferred  in  the  United  States.  It  forms  a  lighter 
colored  powder  than  the  other  varieties.  Ginger  contains  a 
volatile  oil,  a  pungent  resin,  starch,  gum,  and  the  usual  plant 
constituents.  The  volatile  oil  has  the  odor  but  not  the  pun- 
gency of  ginger. 

Adulteration. — The  most  common  adulteration  of  ginger  is 
admixture  with  ginger  that  has  been  exhausted  with  dilute 
alcohol  or  water.  For  the  detection  of  this,  indications  are 
furnished  by  the  determination  of  the  cold-water  extract  taken 
in  conjunction  with  the  soluble  ash,  as  suggested  by  A.  H. 
Allen  and  C.  G.  Moor.  The  following  are  some  results  ob- 
tained : 

JAMAICA. 
a.  b.  COCHIN.  AFRICAN. 

Moisture 13.9  12.7  13.5  15.9 

Total  ash, 3.9  3.2  3.8  3.6 

Soluble  ash,    ....    3.0  1.7  2.0  2.2 

Cold-water  extract,    .14.4  12.2  8.6  10.8 

Neither  the  soluble  ash  nor  the  cold-water  extract  alone 
will  afford  a  means  of  deciding  as  to  the  presence  of  exhausted 
ginger,  but  by  a  combination  of  the  two  data  it  is  possible 
to  arrive  at  a  positive  conclusion.  Thus,  there  is  no  diffi- 
culty in  ascertaining  the  presence  of  the  adulterant  when  it 
has  been  added  in  such  quantities  as  to  bring  the  soluble  ash 
down  to  about  I  per  cent,  and  the  cold-water  extract  to  less 
than  8  per  cent.  Stock  recommends  also  a  determination  of 
the  amount  of  potassium.  The  following  are  some  results 
obtained  by  him  : 

SOLUBLE  ASH.        POTASSIUM. 

Pure  ground  ginger  (94  samples),  .  1.7  to  3.6         0.7      to  1.5 
Exhausted  ginger, 0.2  to  1.6         0.016100.7 


NUTMEG  3O7 

Turmeric,  flour,  ground  husks  and  shells,  seeds,  or  seed- 
cake are  possible  adulterants  of  ginger,  and  are  best  detected 
by  means  of  the  microscope.  The  form  of  the  starch  granules 
present  will  often  furnish  valuable  indications. 

Comparison  with  the  following  figures,  obtained  by  the 
examination  of  pure  samples,  may  also  aid  in  some  cases  : 

RICHARDSON.  KONIG. 

Water, 9.0    to  il.o  10.171012.08 


Ash, 3.39 

Volatile  oil, 0.96 

Fixed  ether-extract,      .    .    2.29 

Starch, 46.16 

Crude  fiber 1.70 

Proteids,     ......    5.25 


7.02  3.79 

2.54  1.68 

4-58  3-44 

53-33  45-70 

7-65  4.36 

10.85  7-12 


6.74 
2.70 

3-53 

54.60 

8.88 

8.34 


NUTMEG 

Nutmeg  is  the  kernel  of  the  seed  of  the  Myristica  fragrans 
Houttyn,  of  the  order  Myristicaccce.  The  fruit  is  gathered 
and  dried  by  slow  heating,  after  which  the  shell  is  removed 
and  the  inclosed  nutmeg  usually  is  coated  by  dipping  in  thick 
milk  of  lime.  The  nutmeg  is  oval  or  elliptical  and  about  an 
inch  in  length.  It  has  a  strong,  pleasant  odor  and  warm, 
aromatic,  somewhat  bitter  taste.  Nutmegs  contain  between 
3  and  5  per  cent,  of  volatile  oil,  considerable  fat,  starch,  and 
proteids.  The  volatile  oil  is  colorless  or  pale  yellow  and  of 
specific  gravity  0.92  to  0.95.  It  is  freely  soluble  in  alcohol 
and  commences  to  boil  at  1 60°.  It  is  dextrorotatory. 
According  to  Cloez,  the  most  volatile  portion  is  a  terpene  and 
is  levorotatory.  There  is  present  also  myristicol,  dextro- 
rotatory and  boiling  at  224°.  On  standing,  myristic  acid 
sometimes  separates  from  the  volatile  oil. 

Adulteration. — Nutmeg  is  little  subject  to  adulteration, 
being  almost  exclusively  sold  unground.  Artificial  nutmegs, 
containing  some  nutmeg  oil,  are  said  to  have  been  prepared 
from  starchy  or  mineral  matter,  but  such  imitation  would 


3O8  FOOD    ANALYSIS 

readily  be  detected  by  the  appearance  of  the  cross -section 
compared  with  that  of  a  genuine  sample. 

The  following  are  the  results  of  some  analyses  by  Richard- 


FIXED  ETHERT 

DESCRIPTION.    WATER.        ASH.       VOL.  OIL.     EXTRACT.        FIBER.  NITROGEN. 

Whole  6.08  3.27  2.84  34-37  11-30  0.83 

Ground         4.19  2.22  3.97  37.30  6.78  0.87 

6.40  3.15  2.90  30.98  9.55  0.84 


For  methods  of  analysis,  see  under  "  Cloves." 


MACE 

Mace  is  the  dried  mantle  or  arillus  of  the  nutmeg.  It 
consists  of  smooth  branching  bands  about  40  mm.  long, 
2  mm.  at  the  base,  and  thinner  above.  It  is  brownish,  has  an 
odor  like  nutmeg,  and  a  warm  aromatic  taste.  Mace  contains 
a  volatile  oil  and  a  resin.  It  is  stated  that  it  contains  no  fat, 
but  this  does  not  accord  with  Spath's  statement,  given  below. 
According  to  Fliickiger,  there  is  also  present  an  uncrystal- 
lizable  sugar  and  a  body  that  turns  blue  with  iodin,  and,  after 
drying,  reddish-violet.  It  appears  to  be  intermediate  between 
starch  and  mucilage. 

Adulteration. — In  addition  to  the  usual  spice  adulterants, 
mace  is  liable  to  contain  Bombay  mace,  a  variety  which 
contains  neither  the  fragrance  nor  the  taste  of  true  mace. 
Starch-containing  adulterants  maybe  detected  by  the  fact  that 
pure  mace,  boiled  with  water,  yields  an  easily  filtered  solution, 
which  is  not  blued  by  iodin.  Determination  of  the  amount 
of  starch  will  furnish  a  rough  indication  of  the  proportion  of 
adulterant  present.  False  or  Bombay  mace  may  be  distin- 
guished by  the  altered  proportion  of  volatile  oil  and  of  ether- 
extract.  The  following  are  some  results  obtained  from  true 
or  Java  mace  compared  with  a  sample  of  false  mace  : 


MACE  309 


• 

FIXED 
ETHER- 

WATER. 

ASH.    VOL.  OIL. 

EXTRACT. 

FIBER". 

NITROGEN. 

.     5.67 

4.10 

4.04 

27.50 

8-93 

0-73 

.     4-86 

2.65 

8.66 

29.08 

4.48 

0.98 

.  10.47 

2.  2O 

8.68 

23-33 

6.88 

o.8l 

.  18.21 

1.62 

3  37 

21.90 

3-70 

.    . 

.    7.04 

1.36 

0.27 

56.75 

8.17 

.    . 

True  mace, 


Bombay  mace, 

E.  Spath  extracted  a  number  of  samples  of  mace  with 
petroleum  spirit  and  determined  the  constants  of  the  material 
obtained.  The  figures  obtained  from  mace  from  Banda, 
Menado,  Penang,  Macassar,  and  Zanzibar  closely  agreed  with 
each  other : 

MELTING-  ZEISS  MEISSL 

POINT  SAPONI-  REFRACTO-  COEFFICIENT  NUMBER 

IN  OPEN  FICATION  lODIN        METER              OF              (BANDA 

TUBE.  NUMBER.-'  NUMBER.     AT  40°.    REFRACTION.    MACE). 

True  mace,  .  .  25-26  169.9-173  75.6-80.8  76-85  1.480-1.487  4.1-4.2 
Bombaymace,  .  31-31.5  189.4-191.4  50.4-53.5  48-49  1.463-1.464  i.o-i.i 
From  m  a  c  e  - 

scales,      i.f.t 

"the  covering 

inside  the 

seed-mantle,"  28.5-29       148.2-148.8  71.3-73.4      .    . 


According  to  Konig,  a  sample  containing  less  than  3  per 
cent,  of  volatile  oil  or  more  than  35  per  cent,  of  extract  on  the 
dry  substance  cannot  be  regarded  as  true  mace.  False  mace 
is  also  distinguished  by  the  presence  of  a  peculiar  coloring- 
matter,  analogous  to  that  of  turmeric,  rather  freely  soluble  in 
alcohol  and  but  slightly  soluble  in  ether.  The  large  oil  cells 
of  the  false  mace  contain,  according  to  Hanausek,  a  resinous 
body  with  which  alcohol  produces  a  yellow  or  greenish-yellow 
solution,  turned  orange-red  by  alkalies.  If  10  to  20  c.c.  of 
alcohol  are  shaken  with  2  or  3  grams  of  powdered  mace  for 
a  few  minutes  and  the  liquid  filtered,  the  filtrate,  but  not  the 
filter-paper,  becomes  colored.  In  the  case  of  false  mace  the 
strongly  colored  filtrate  dyes  the  paper  a  fixed  yellow.  If  the 
filter  is  dried,  freed  from  the  attached  powder,  and  touched 
with  a  weak  alkaline  solution,  the  presence  of  turmeric  is  indi- 


3IO  FOOD    ANALYSIS 

cated  by  a  brown,  and  of  false  mace  by  a  blood-red,  color. 
If  the  alkali  be  removed  by  washing  the  filter  with  water, 
a  trace  of  acid  will  be  sufficient  to  bring  back  the  yellow. 
Hefelman  suggests  decomposing  an  alcoholic  extract  with 
lead  acetate.  Genuine  mace  gives  a  milk-white  turbidity ; 
false  mace,  even  when  mixed  with  a  large  proportion  of  true 
mace,  gives  a  red  flocculent  precipitate.  Turmeric  produces 
a  somewhat  similar  color.  If  a  strip  of  filter-paper  be  dipped 
into  the  alcoholic  extract,  gently  dried,  and  then  drawn 
through  a  cold  saturated  solution  of  boric  acid  in  water,  the 
presence  of  a  very  small  quantity  of  turmeric  will  be  indicated 
by  an  orange  or  red-brown  tint.  With  false  mace,  on  the 
other  hand,  the  yellow  color  of  the  paper  will  remain  un- 
changed. 

P.  Soltsien  has  called  attention  to  the  difference  between 
Bombay  and  Banda  mace  as  regards  the  quantity  of  matter 
extracted  by  ether  after  removal  of  the  fat-like  bodies  by 
petroleum  spirit,  and  suggests  that  advantage  be  taken  of  the 
fact  in  order  to  distinguish  between  the  two.  The  difference 
is  very  considerable,  the  quantity  being  about  ten  times  as 
great  with  Bombay  mace  as  with  true  mace.  Soltsien  has 
never  found  more  than  4,8  per  cent,  of  matter  extracted  by 
ether  in  a  pure  Banda  mace  and  suggested  5.5  per  cent,  as  a 
maximum. 

The  manipulation  is  carried  out  as  follows:  10  grams  of 
powdered  mace  are  exhausted  by  boiling  petroleum  spirit  in 
an  extraction  apparatus.  On  cooling,  an  oily  portion  tends 
to  separate  at  the  bottom  of  the  vessel,  and  this  belongs  prop- 
erly to  the  extractive  matter  soluble  in  ether.  The  petroleum 
extract  is  poured  off,  the  separated  oily  portion  in  the  flask 
washed  with  petroleum  spirit  and  dissolved  in  absolute  ether, 
and  then  a  second  extraction  is  made  with  boiling  ether.  In 
the  ether-extract  there  is  also  a  tendency  for  a  portion  to  sep- 
arate out.  The  extract  is  poured  off,  the  separated  matter 


,  ALLSPICE  3 1  I 

washed  with  ether,  and  the  washing  added  to  the  extract, 
which  is  then  filtered,  evaporated,  and  dried  in  the  water- 
bath,  the  residue  being  weighed. 


ALLSPICE 

Allspice  or  pimento  is  the  dried,  nearly  ripe  fruit  of  the 
Eugenia  pimehta  DeC.  It  is  nearly  globular,  6  mm.  or  less 
in  diameter.  Allspice  contains  volatile  oil,  fixed  oil,  resin, 
tannin,  starch,  sugar,  and  mucilage.  The  volatile  oil  is  simi- 
lar in  composition  and  general  properties  to  oil  of  cloves.  The 
yield  is  usually  between  3  and  4  per  cent. 

Adulteration. — On  account  of  its  cheapness,  allspice  is  less 
subject  to  adulteration  than  other  spices.  In  addition  to  the 
usual  spice  admixtures,  clove  stems  and  the  lowest  grades  of 
cloVes  are  sometimes  added.  These  latter  may  be  detected 
by  the  microscope,  and  also,  in  some  cases,  by  the  greatly 
increased  proportion  of  volatile  oil. 

The  following  results  from  a  sample  of  whole  allspice  are 
given  by  Richardson  : 

FIXED  ETHER 
WATER.  ASH.  VOL.  OIL.        RESIDUE.     CRUDE  FIBER.    NITROGEN. 

6.19  4.01  5.15  6.15  14-83  0.70 

According  to  figures  published  by  the  A.  O.  A.  C.,  the 
variations  in  composition  of  pure  samples  will  usually  range 
within  the  following  limits  : 

PER  CENT. 

Moisture, 5.5  to  12 

Ash 3     to    5 

Volatile  oil, 2     to    5 

Ether  extract, 7      to  13 

Fiber, 13      to  22 

A  sample  of  pure,  whole  Jamaica  allspice  examined  by  A. 
L.  Winton  gave  the  following  results  : 

Volatile  oil,  3.52  ;  non-volatile  ether  extract,  6.48;  ash,  4.57. 


312  FOOD    ANALYSIS 

12    samples    of  commercial  ground  allspice,  in  which  no 
adulterant  could  be  detected,  gave  results  as  follows  : 

Volatile  oil, 2.05  to  2.84 

Non-volatile  ether-extract, 3.98  to  5.62 

Ash, 4.62  to  5.50 

Analytic  Methods. — Moisture,  volatile  oil,  and  fixed  ether- 
extract   are  determined   as  described   under  cloves  (p.  316). 


CINNAMON 

Cinnamon  is  the  inner  bark  of  several  species  of  Cinnamo- 
mumt  of  the  order  Lauracece.  Commercial  cinnamon  may  be 
divided  into  three  classes,  as  follows : 

1.  True  or  Ceylon  cinnamon,  from   C.  Zeylanicum  Nees. 
This  is  the  finest  quality,  and  is  the  one  which  is  official  in 
most  pharmacopeias.      It  is  rarely  found  in  the  grocery  trade, 
and  is  used  as  a  drug.      In  its  preparation  for  the  market  it  is 
deprived  entirely  of  the  outer  coating  and  inner  cortical  lay- 
ers, and  forms  long  strips,  usually  not  above  the  thickness  of 
stout  writing-paper. 

2.  Common  or   Chinese   cinnamon,   C.  cassia  Blum.,   and 
known  as  cinnamon  cassia  or  cassia  bark.     It  is  thicker  than 
true  cinnamon  and  generally  covered  with  patches  of  cork. 
It  has  a  less  delicate  and  more  astringent  taste  than  true  cin- 
namon.     The  variety  of   cassia    known  as    Saigon  cassia  is 
said  to  have  greater  strength  than  true  cinnamon. 

3.  Cinnamon    barks    from  various    unidentified  species  or 
varieties,   including    inferior  qualities  obtained    in    the    East 
Indies  and  adjacent  mainlands.      It  is  from  these    that   the 
common   ground    cinnamon   of  the    retail   trade    is    usually 
prepared. 

Microscopically,  true  cinnamon  may  be  distinguished  from 
cassia  by  the  presence  in  the  former  of  long  cells  of  woody 
fiber,  which  are  especially  well  shown  under  polarized  light. 


CINNAMON 

The  following  are  some  analyses  of  pure  samples  : 


313 


ANALYST. 

WATER 

ETHE- 
REAL 
OIL. 

FIXED 
ETHER 
EX- 
TRACT. 

CRUDE 
FIBER. 

NITRO- 
GEN. 

ASH. 

Konig  and  Krauch 

Ceylon  cinna- 
mon,  .    .    . 

12.44 

1-45 

35-46 

0.64 

3-28 

C.  Richardson 

Ceylon  cinna- 
mon, .    .    . 

10.00 

3-14 

3-30 

16.18 

o.6l 

3-70 

tt 

Ceylon  cinna- 
mon, .    .    . 

5-40 

1.05 

1.66 

33-08 

0.48 

4-55 

<( 

Ceylon  cinna- 
mon, .    .    . 

7-93 

0.82 

1.58 

25-63 

0.62 

3-40 

Konig  and  Krauch 

Cassia  bark,  . 

13-95 

•    • 

3-26 

17.72 

0.62 

2.22 

<<                   «< 

«        « 

14.44 

1.24 

17.76 

0.46 

1.96 

C.  Richardson 

«        « 

9.42 

58 

1.40 

17-73 

0-45 

2-35 

'      " 

«        « 

11.04 

1.  21 

1.86 

15.45 

0.72 

2.48 

«  < 

«        « 

17-45 

o-55 

0.74 

14-33 

0.64 

5-25 

The  ash  of  pure  cinnamon  is  usually  white,  while  that  of 
cassia  is  often  brown,  due  to  the  larger  proportion  of  man- 
ganese oxid. 

The  following  results  were  obtained  by  Dyer  and  Gilbard, 
on  5  samples  of  pure  cinnamon  :  . 

ALCO- 

FIXED  HOL  Ex-     TOTAL       ASH         ASH 
MOISTURE  VOLATILE  ETHER  TRACT v      ASH,     SOLUBLE    INSOL. 

(LOSS   AT  OIL  EX-        AFTER  LESS  IN  IN  NlTRO- 

IOO°).       (APPROX.).    TRACT.    ETHER.         SAND.      WATER.    WATER.         FIBER.  GEN. 

11.33        °-77         1-87       ii. o        2.97        o.io      2.07        32.90        0.42 
to  to  to  to  to  to  to  to  to 

13.00  1.93  2.30        13.27  5.00  0.90          4.70  35.67  0.54 

Ground  walnut  shells  gave  following  results  : 

9.97       0.27       i. 60     3.67       0.87       0.37     0.50       47.67       0.20 

The  items  volatile  oil,  alcohol-extract,  insoluble  ash,  and 
27 


314  FOOD    ANALYSIS 

nitrogen  appear  to  furnish  the  most  assistance  in  determining 
the  proportion  of  admixture. 

The  chemical  composition  of  cinnamon  and  cassia  is  in  the 
main  the  same.  Each  contains  a  volatile  oil,  tannin,  sugar, 
mannite,  starch,  and  mucilage.  The  essential  oil  of  C.  Zeylan- 
icum  is  pale  yellow  or  reddish,  becoming  darker  and  thicker 
on  exposure,  and  finally  depositing  crystals  of  cinnamic  acid. 
It  has  a  strong  odor  of  cinnamon  and  a  sweet,  warm,  aromatic 
taste.  The  specific  gravity  of  the  fresh  oil  is  1.035.  I*1  some 
cases  it  is  slightly  levorotatory.  The  essential  oil  of  cassia 
has  similar  properties,  but  its  color  is  more  brownish,  taste 
less  sweet,  odor  less  delicate,  specific  gravity  greater  (1.055  to 
1.065),  and  is  sometimes  slightly  dextrorotatory.  Both  oils 
contain  variable  quantities  of  hydrocarbons,  but  consist  chiefly 
of  cinnamic  aldehyde,  and,  when  old,  contain  resin  and  cinna- 
mic acid. 

Adulteration. — The  chief  adulteration  consists  in  the  substi- 
tution of  the  inferior  cassia  for  the  true  cinnamon.  As  noted 
above,  the  true  cinnamon  is  now  only  obtained  as  a  drug. 
They  may  be  distinguished  by  the  difference  in  their  micro- 
scopic characters.  Aside  from  this,  the  most  important 
adulteration  consists  in  the  partial  abstraction  of  the  ethereal 
oil,  on  which  the  value  of  the  spice  depends,  either  by  alcohol 
or  by  distillation  with  water.  Sophistication  of  this  kind  is 
difficult  to  detect,  by  reason  of  the  variations  of  the  original 
bark  in  composition.  The  lower  grades  of  ground  cinnamon 
are  also  adulterated  with  barks  of  allied  species,  refuse  found 
in  the  bundles  of  cinnamon  as  imported,  mahogany  and  other 
woods,  flours  of  various  kinds,  oil-cake,  and  similar  materials. 
These  are  often  readily  detected  by  the  microscope. 

In  Austria,  Bavaria,  and  Switzerland,  cinnamon  or  cassia 
containing  more  than  5  per  cent,  of  ash  or  I  per  cent,  of 
sand  is  held  to  be  adulterated. 


CLOVES  3 i 5 

CLOVES 

Cloves  are  the  unexpanded  flower  of  the  Eugenia  aromatica 
O.  Kuntze,  of  the  order  Myrtacece.  They  consist  of  a  dark 
brown,  cylindrical  calyx,  3  to  4  mm.  thick,  bearing  a  several- 
celled  ovary  and  a  globular  head  of  four  petals.  Many  oil 
glands  are  under  the  epidermis. 

Cloves  contain  a  volatile  oil,  resin,  tannin,  and  gum,  but  no 
starch.  The  volatile  oil  is  thicker  than  most  essential  oils  and 
becomes  still  thicker  and  darker  with  age.  It  has  the  odor  of 
cloves  and  a  burning  aromatic  taste.  Its  specific  gravity  is 
from  1.034  to  1.056  ;  it  boils  at  240°.  The  oil  obtained  from 
clove  stalks  has  a  specific  gravity  of  1.009.  Oil  of  cloves 
dissolves  freely  in  alcohol.  Strong  solution  of  potassium 
hydroxid  converts  it  into  a  crystalline  mass  of  potassium 
eugenate.  It  is  sometimes  slightly  dextrorotatory.  It  con- 
sists principally  of  a  hydrocarbon  and  eugenol  (eugenic 
acid).  On  distilling  a  mixture  of  cloves  and  potassium  hy- 
droxid solution,  the  hydrocarbon  is  obtained  as  an  oil  of 
specific  gravity  0.918,  boiling  at  251°.  By  decomposing 
potassium  eugenate  with  sulfuric  acid  and  distilling,  eugenic 
acid  is  obtained  as  a  colorless  oil  of  specific  gravity  from  1.076 
to  1.078,  boiling  at  247.5°.  Caryophyllin  and  a  salicylic  ester 
have  also  been  found. 

Adulterations. — In  addition  to  the  adulterants  usually  em- 
ployed for  ground  spices,  clove  stems  and  the  fruit  of  the  clove, 
the  so-called  "  mother  cloves,"  may  be  added.  The  analysis 
of  a  sample  of  clove  stems  is  given  below.  They  may  be 
detected  by  the  microscope  by  the  presence  of  numerous 
stone  cells,  bast  fibers,  and  scaliform  ducts.  The  form  of  the 
stone  cells  varies  greatly  ;  the  walls  are  thick  and  the  interior 
cavity  may  be  simple  or  ramifying.  The  bast  fibers  are  usually 
long,  spindle-shaped,  and  thick.  The  scaliform  ducts,  together 
with  the  stone  cells,  are  the  best  evidence  of  the  presence  of 


310  FOOD    ANALYSIS 

clove  stems.  In  mother-cloves,  the  stone  cells  are  very  thick- 
walled  and  have  a  nodulated  exterior,  which  enables  them  to 
be  distinguished  easily.  The  seeds  contain  starch  and 
raphides.  The  starch  granules  resemble  those  of  some  kinds 
of  arrow-root ;  they  are  principally  pear-shaped,  or,  rather, 
slender  and  slightly  curved,  generally  single,  and  show  a  well- 
marked  cross  under  polarized  light.  There  is  a  small  hilum 
at  the  broad  end.  The  resemblance  to  arrowroot  starch  is 
not  likely  to  cause  confusion,  as  the  latter  is  too  costly  for  use 
as  an  adulterant. 

Cloves  are  also  adulterated  by  the  addition  of  samples  from 
which  a  portion  of  the  essential  oil  has  been  removed.  This 
is  usually  difficult  of  detection  on  account  of  the  great  varia- 
tion in  the  amount  of  oil  found  in  pure  samples. 


ANALYSES  OF  CLOVES  AND  STEMS 


WHOLE  CLOVES. 

STEMS. 

Water          

16.39 
4.84 
16.98 
6.  20 
10.56 

o-95 
Laube  and 
Allendorf 

2.90  to  10.67 
5.25  '    13-05 
10.23  '    18.89 
7.12  '    10.24 
6.18*      9.75 

0.76  '        1.  12 

Richardson, 
7  samples 

9  to  21 
Dietsch 

10.18 
6.96 
4.40 
4-03 
I3-58 
0.92 
Richardson 

Ash,    
Volatile  Oil         

Fixed  ether-residue,  .... 
Crude  fiber,     
Nitrogen 

Analyst,  

In  20  samples,  either  known  to  be  pure,  or  in  which  no 
adulteration  could  be  detected  by  the  microscope,  A.  L.  Win- 
ton  found  the  following  range  in  composition  : 

PER  CENT. 

Volatile  oil, .10.01101832 

Fixed  ether-extract, 4.90  "    6.20 

Ash, 6.50  "    7.95 

ANALYTIC  METHODS. — The  presence  of  a  large  amount  of 
volatile  oil  necessitates  a  departure  from  the  methods  usually 


MUSTARD  3J7 

employed  for  spices.  The  following  method  for  non-volatile 
ether-extract  and  volatile  oil  is  practically  the  same  as  that 
adopted  by  C.  Richardson  and  A.  L.  Winton  :  2  grams  of 
the  material  are  weighed  into  a  fat-free  paper  thimble,  which, 
with  its  contents,  is  dried  by  standing  in  a  desiccator  over  sul- 
furic  acid  for  16  hours,  after  which  the  ether-soluble  matters 
are  extracted  as  described  on  page  49.  The  ethereal  solu- 
tion is  transferred  to  a  tared  receptacle  and  allowed  to  evapo- 
rate at  the  ordinary  temperature.  After  standing  18  hours 
over  sulfuric  acid,  the  total  ether-extract  is  weighed.  It  is 
then  heated  first  at  100°  for  6  hours,  and  then  at  1 10°, 
until  the  weight  becomes  constant,  the  loss  being  volatile 
oil,  and  the  residue  the  fat  and  resin.  The  fiber  may  be 
determined  as  usual  on  the  residue  insoluble  in  ether  (p.  46). 


MUSTARD 

Mustard  is  prepared  from  the  seeds  of  the  Brassica  nigra 
Koch  (black  mustard)  and  B.  alba  Hkr.  f.  (white  mustard). 
Commercial  mustard  may  be  a  mixture  of  the  two  forms.  The 
seeds  are  finely  powdered  and  passed  through  a  sieve  in  order 
to  remove  husks.  Both  forms  contain  a  fixed  oil  in  fairly  con- 
stant proportion,  albuminous  matter,  gum,  sinapin  thiocyanate, 
and  an  enzym,  myrosin,  but  no  starch.  White  mustard  con- 
tains also  the  glucosid,  sinalbin  ;  and  black  mustard  the  glu- 
cosid,  potassium  myronate.  These  glucosids  are  decomposed 
by  the  enzym,  on  addition  of  water,  but  the  action  is  not 
hydrolytic. 

Allyl  isothiocyanate,  volatile  oil  of  mustard,  is  a  colorless 
liquid,  specific  gravity  j*0  1.018,  boiling  at  148-150°,  and 
volatile  in  a  current  of  steam.  It  has  a  strong  mustard-like 
odor  and  the  vapor  excites  a  flow  of  tears.  It  is  slightly  sol- 
uble in  water  and  much  more  so  in  alcohol,  ether,  petroleum 


FOOD    ANALYSIS 

spirit,  and  carbon  disulfid.  It  is  a  powerful  rubefacient  and 
vesicant. 

Acrinyl  isothiocyanate  is  a  yellow  liquid  of  pungent  burning 
taste.  It  is  a  less  powerful  vesicant  than  the  oil  from  black 
mustard  and  is  but  slightly  volatile  in  steam.  It  is  insoluble 
in  water,  but  soluble  in  alcohol  and  ether. 

Black  mustard  seeds  do  not  contain  sufficient  myrosin  to 
convert  all  of  the  potassium  myronate  present.  White  mus- 
tard seeds,  on  the  contrary,  contain  more  myrosin  than  is 
required  to  convert  the  sinalbin,  so  that  by  a  judicious  mixture 
of  the  two  a  greater  yield  of  allyl  isothiocyanate  is  secured. 
White  mustard  yields  only  traces. 

Myrosin  is  coagulated  by  heat,  so  that  if  mustard  be  intro- 
duced into  boiling  water,  no  volatile  oil  is  produced.  It  is 
said  to  recover  its  converting  power  by  immersion  in  water 
for  some  days. 

The  fixed  oil  of  mustard  has  the  following  physical  and 
chemical  constants  :  Sp.  gr.,  -^-,  0.914  to  0.920 ;  saponifica- 
tion  value,  170  to  175  ;  iodin  value,  92  to  106.  About  35 
per  cent,  is  usually  present.  Commercial  samples  of  good 
quality  may  contain  much  less,  a  portion  having  been  ex- 
pressed in  the  manufacture  of  the  mustard  flour. 

The  following  are  some  results  of  examination  of  pure 
samples  : 

Mean  of  three  closely  concordant  analyses  of  white  mustard 
by  Leeds  and  Everhart : 

Water, 6. 83  per  cent. 

Potassium  myronate, 0.64 

Sinapin  thiocyanate, 11.12 

Myrosin  and  albumin, 28.48 

Fixed  oil, ,    ....  29.21 

Ash, 3.75 

Variations  in  composition  of  ground  mustard  seeds,  accord- 
ing to  figures  published  by  A.  O.  A.  C. : 


FLAVORING    EXTRACTS  319 

PER  CENT. 

Moisture, 3  to    8 

Ash, 4  to    7 

Ether-extract, 31  to  37 

Fiber, 4  to    6.5 

Aqueous  extract, 30  to  38 

Sulfur, I  to    1.6 

When  prepared  from  partially  expressed  seeds,  the  mustard 
will  contain  less  oil  (ether-extract)  and  a  correspondingly 
larger  proportion  of  the  other  ingredients. 

Adulteration. — The  most  common  adulterant  for  mustard  is 
rice  flour  or  wheat  flour.  These  are  readily  detected  by  the 
microscope  and  by  the  presence  of  starch.  This  may  also  be 
present  as  a  constituent  of  turmeric,  added  to  color  pale 
samples.  Starch  may  be  detected  by  boiling  a  portion  of  the 
sample  with  water,  filtering,  and  adding  iodin  to  the  filtrate. 
It  is  estimated  as  on  page  97.  The  proportion  of  starch  in 
wheat  flour  is  about  72  per  cent.  A.  H.  Allen  suggests  the 
determination  of  the  amount  of  fixed  oil,  which  is  usually  about 
35  per  cent.,  and  calculating  from  its  deficiency  the  proportion 
of  diluent  present.  In  view  of  the  practice  of  some  manu- 
facturers of  pressing  the  seed,  such  a  method  is  no  longer 
reliable,  but  may  often  be  of  value  as  corroborative  evidence. 

Of  mineral  additions,  calcium  sulfate,  chalk,  and  lead 
chromate  have  been  employed.  These  are  detected  in  the 
ash. 

Yellow  coloring-matters  are  frequently  employed,  the  most 
common  being  turmeric,  Martius'  yellow,  and  naphthol  yel- 
low S.  Coal-tar  colors  may  be  detected  by  methods  given 
on  pages  77—82  ;  turmeric,  by  the  test  given  under  "  Mace" 
or  by  the  principle  of  the  test  for  boric  acid,  page  89. 

FLAVORING    EXTRACTS 

Vanilla  Extract. — The  highest  grade  of  this  preparation 
is  obtained  by  macerating  vanilla  beans  with  alcohol  of  50  per 


32O  FOOD    ANALYSIS 

cent.  The  cheaper  grades  contain  cumarin,  artificial  vanillin, 
some  glycerol,  and  caramel  or  coal-tar  colors.  The  cumarin 
may  be  either  added  as  such  or  obtained  by  macerating  tonka 
beans  in  the  solvent.  In  cheap  extracts  a  very  dilute  alcohol 
is  used  and  the  solvent  action  aided  by  some  alkaline  substance, 
generally  acid  potassium  carbonate.  The  following  is  a  pub- 
lished formula  for  a  very  cheap  imitation  extract  : 

Vanillin,      I  gram 

Cumarin, I  gram 

Alcohol, 125  c.c. 

Glycerol,     65  c.c. 

Water, I  liter 

Caramel  to  color. 

Commercial  vanilla  extracts  have  been  examined  by  W.  H. 
Hess.  He  gives  the  following  test  as  a  critical  one  in  dis- 
tinguishing true  from  imitation  extracts  :  A  portion  of  the 
sample  should  be  mixed  with  a  few  drops  of  lead  acetate 
solution;  if  a  bulky  flocculent  precipitate  does  not  form,  the 
extract  is  not  of  high  quality.  •  The  process  given  by  Hess 
may  then  be  applied  to  establish  its  general  character  : 

5  c.c.  of  the  extract  are  diluted  slowly  with  10  c.c.  of 
water  and  the  mixture  shaken.  A  flocculent  reddish-brown 
precipitate  shows  that  no  alkali  has  been  added.  A  milky 
solution  indicates  a  foreign  resin.  Hydrochloric  acid  is  added 
drop  by  drop  to  a  portion  of  the  diluted  liquid  ;  only  a  slight 
turbidity  should  result.  If  the  turbidity  is  considerable  and 
the  color  fades,  alkali  has  been  employed  in  making  the 
extract. 

25  c.c.  of  the  sample  are  concentrated  on  a  water-bath 
until  the  alcohol  is  removed  and  made  up  to  the  original 
volume  with  water.  The  vanilla  resin  will  appear  as  an 
amorphous,  flocculent,  reddish-brown  mass  if  alkali  be  absent. 
The  cold  solution  is  acidified  with  hydrochloric  acid,  when 
the  whole  of  the  resin  will  separate,  leaving  the  liquid  nearly 
colorless.  After  standing  several  hours  the  residue  may  be 


FLAVORING    EXTRACTS  321 

collected  on  a  filter,  washed  with  water,  and  the  filtrate  and 
precipitate  further  tested. 

A  piece  of  the  filter  with  resin  attached  is  placed  in  sodium 
hydroxid  solution.  A  deep  red  solution  should  be  formed. 
A  solution  of  a  portion  of  the  precipitate  in  alcohol  should 
not  give  any  marked  reaction  with  ferric  chlorid  or  hydro- 
chloric acid. 

A  portion  of  the  filtrate  is  concentrated  at  a  low  tempera- 
ture until  its  color  approximates  that  of  the  original  sample, 
a  few  drops  of  strong  hydrochloric  acid  are  added,  and  gently 
heated.  Caramel  will  produce  a  yellowish-red  flocculent  pre- 
cipitate. The  liquid  is  allowed  to  cool,  filtered,  and  the 
precipitate  washed  with  water  ;  if  from  caramel,  the  precipitate 
will  be  insoluble  in  water,  alcohol,  and  ether,  soluble  in 
sodium  hydroxid,  glacial  acetic  acid,  and  dilute  alcohol. 

&  small  portion  of  the  filtrate  is  made  alkaline  with  am- 
monium hydroxid ;  natural  color  is  much  deepened.  Zinc 
dust  is  added,  and  the  liquid  warmed  gently.  The  color 
should  return  to  about  the  tint  it  possessed  before  the  am- 
monium hydroxid  was  added,  but  azo-colors  will  be  com- 
pletely bleached.  If  the  latter  effect  occurs,  some  of  the 
liquid  should  be  mixed  with  hydrogen  dioxid,  when  the  color 
will  return. 

The  caramel  test  described  on  page  1 30  will  probably  be  of 
service  in  these  examinations. 

Detection  of  Cumarin  and  Vanillin. — 50  c.c.  of  the  sample 
are  evaporated  at  low  temperature,  with  addition  of  water 
from  time  to  time,  until  the  alcohol  is  removed.  Lead  acetate 
solution  is  added  slowly,  with  constant  stirring,  until  precipi- 
tation ceases.  The  liquid  is  filtered,  the  precipitate  washed 
with  a  few  c.c.  of  hot  water,  the  filtrate  cooled,  and  agitated 
with  successive  portions,  20  c.c.  each,  of  chloroform  until  a 
few  drops  of  the  latter  leave  no  residue  when  evaporated  on 
a  watch-glass.  Four  extractions  will  usually  be  sufficient. 
28 


322  FOOD    ANALYSIS 

The  chloroform  extracts  are  mixed  and  shaken  with  successive 
portions,  2  c.c.  each,  of  ammonium  hydroxid  solution,  sp.  gr. 
0.960,  until  the  latter  no  longer  becomes  yellow.  Vanillin 
dissolves  in  the  ammoniacal  solution,  while  the  cumarin 
remains  in  the  chloroform. 

The  chloroform  is  evaporated,  best  under  reduced  pressure, 
and  the  residue  dried,  either  at  low  pressure  over  sulfuric 
acid,  or  in  an  air-bath  not  over  45°,  is  repeatedly  extracted 
with  very  light  petroleum  (so-called  ligroin),  boiling  about 
35°,  until  a  drop  of  the  solvent  leaves  no  residue.  The  col- 
lected ligroin  solutions  are  evaporated  and  (best  at  low 
pressure)  dried  at  not  above  45°.  The  residue  is  cumarin. 
The  melting-point  (67°)  and  odor  will  serve  to  confirm  the 
analysis. 

The  ammonium  hydroxid  solution  is  rendered  slightly  acid 
with  hydrochloric  acid  and  the  vanillin  removed  by  repeated 
agitation  with  chloroform.  The  chloroform  is  evaporated,  the 
residue  dried  at  not  above  55°,  and  washed  repeatedly  with 
small  portions -of  ligroin,  the  portions  collected  evaporated  as 
before,  and  the  residue,  vanillin,  is  weighed.  It  may  be 
identified  by  melting-point  (8o°-8i°)  and  the  other  tests. 
The  process  may  be  simplified  if  merely  the  qualitative 
recognition  of  cumarin  in  commercial  vanilla  extracts  be  re- 
quired. 

Lemon  Juice  and  Lemon  Sirup. — A.  Borntrager  fur- 
nishes the  following  analyses  of  lemon  juice  : 

RIPE  FRUIT.  UNRIPE  FRUIT: 

Citric  acid, 7.25  7.70 

Reducing  sugar, 0.75  0.21 

Sucrose, 0.19  0.78 

Ash, 0.39  0.49 

Total  solids, 8.87  9.30 

Borntrager  also  examined  several  samples  of  lemon 
sirup  giving  the  following  results.  No.  2  has  been  sophis- 
ticated : 


CATSUP    AND    TABLE    ACCESSORIES  323 

No.  i.  No.  2. 

Citric  acid, 14-4°  5-42 

Tartaric  acid, o.oo  10.70 

Reducing  sugar  expressed  as  dextrose,    .30.10  38.42 

Sucrose, o.oo  o.oo 

Ash, 0.32  0.72 

Total  solids, 81.92  80.56 

The  reducing  sugar  may  result  from  the  inversion  of  the 
cane-sugar.  The  following  formula  for  a  cheap  lemon-extract 
is  quoted  from  a  trade  circular  : 

Lemon  oil, I      gram 

Lemon  grass  oil, O.I  c.c. 

Citric  acid, 0.5  c.c. 

Alcohol, 16.0  c.c. 

Water, .    .  no.oc.c. 

Turmeric  tincture  to  color. 


Magnesium  carbonate  is  used  as  a  clarifying  agent,  but  is 
removed  by  filtration.  Artificial  colors,  especially  naphthol 
yellow  S,  are  often  used  as  coloring  agents. 

Analytic  examinations  will  be  usually  directed  to  determine 
the  presence  of  artificial  colors,  glucose,  and  preservatives,  for 
which  see  pages  77,  115,  and  86. 

Tartaric  acid  may  be  determined  as  follows  :  20  grams  of 
the  sirup  are  mixed  with  5  grams  of  potassium  chlorid,  the 
solution  neutralized  with  potassium  hydroxid  and  made  up  to 
50  c.c.  with  water.  5  grams  of  citric  acid  are  added,  the 
solution  well  stirred,  and  allowed  to  stand  overnight.  The 
precipitated  acid  potassium  tartrate  is  washed  first  with  a  satur- 
ated solution  of  the  same  substance,  then  twice  with  a  10 
per  cent,  solution  of  potassium  chlorid,  and  titrated  hot  with 
standard  alkali. 

CATSUP    AND    TABLE   ACCESSORIES 

Catsup  is  prepared  from  the  pulp  of  tomatoes  with  addition 
of  vinegar  and  various  spices.  The  bottled  catsups  almost 
always  contain  artificial  colors  and  preservatives.  The  pre- 


324  FOOD    ANALYSIS 

servative  is  usually  salicylic  acid  or  sodium  benzoate,  but 
boric  acid  may  be  used.  It  must  be  borne  in  mind  that  small 
amounts  of  boric  acid  may  exist  in  some  of  the  materials 
used  in  making  the  catsup,  and  also  that  some  manufacturers 
buy  the  tomato  pulp  from  canning  establishments,  and  this 
may  be  treated  with  a  little  salicylic  acid  to  prevent  it  spoiling 
in  warm  weather.  The  detection  of  artificial  colors  and  pre- 
servatives will  be  attained  by  the  general  processes  given  in 
the  sections  on  those  subjects. 

Many  other  articles,  such  as  pickles,  pickled  onions,  chow- 
chow,  horseradish,  and  sauces,  are  now  sold  in  bottles  or  cans. 
These  are  rarely  colored,  but  may  contain  preservatives, 
especially  salicylic  acid  or  sodium  benzoate,  detected  as  noted 
above. 

Desserts. — Under  this  head  will  be  included  ice-cream, 
water-ices,  jams,  jellies,  marmalades,  fruit  sirups,  fancy  cakes, 
pies,  and  custards.  The  component  parts  of  the  higher  grades 
of  these  articles  will  be  found  in  cook-books.  The  analytic 
investigations  will  be  limited  to  the  detection  of  preservatives, 
artificial  colors,  starch,  gelatin,  and  substitutes  for  cane-sugar. 
The  detection  of  these  substances  is  given  elsewhere,  except  as 
to  gelatin,  for  which  the  following  process  has  been  proposed  : 
The  material  is  boiled  with  water,  filtered,  the  filtrate  boiled 
with  excess  of  potassium  dichromate,  cooled,  and  a  few  drops 
of  sulfuric  acid  added.  If  gelatin  is  present,  a  flocculent  pre- 
cipitate will  be  formed. 

It  is  probable  that  the  reaction  of  gelatin  with  formaldehyde 
could  be  utilized  in  these  examinations. 

Ice-cream  is  not  subject  to  serious  adulteration.  The 
cheaper  grades  contain  much  starch,  and  often  artificial  fla- 
vors and  colors.  In  hot  weather,  milk  and  milk  products 
are  liable  to  become  very  poisonous  by  the  development  of 
bacteria,  and  such  cases  are  often  wrongly  charged  to  adul- 
teration. Ice-cream  and  similar  refreshments  hawked  about 


CATSUP    AND    TABLE    ACCESSORIES  325 

the  streets  of  large  cities  are  very  apt  to  be  dirty,  containing 
bodies  of  insects  and  other  filth. 

The  method  employed  by  L.  K.  Boseley  for  the  analysis 
of  marmalade  will  be  applicable  in  many  cases  to  jams, 
jellies,  and  similar  articles. 

Water. — Several  grams  of  the  well-mixed  sample  are 
weighed  in  a  flat  basin  with  a  glass  rod.  The  mass  is  warmed 
and  5  c.c.  of  40  per  cent,  alcohol  added.  15  grams  of  dry 
quartz  sand  are  stirred  in.  The  dish  is  heated  on  a  water- 
bath  for  one  hour,  5  c.c.  of  absolute  alcohol  added,  and  again 
heated  for  one  hour,  and  then  in  an  air-bath  until  the  weight 
is  practically  constant,  which  may  require  more  than  24 
hours. 

Polarimetric  Examination^. — A  weight  of  the  well-mixed 
sample  equal  to  2.5  times  the  normal  weight  of  the  instru- 
ment to  be  used  (i.  e.,  65.12  for  instruments  adapted  to  a  con- 
centration of  26.048)  is  dissolved  in  about  50  c.c.  of  cold 
water,  added  in  small  portions  with  stirring,  transferred  to  a 
250  c.c.  flask,  the  residue  washed,  and  the  washings  added 
to  the  contents  of  the  flask.  Lead  subacetate  is  added  in 
amount  not  quite  sufficient  to  remove  the  acidity,  the  flask 
filled  to  the  mark  and  the  liquid  passed  through  a  dry  filter, 
the  first  20  c.c.  rejected,  and  the  polarimetric  reading  of  a  por- 
tion of  the  remainder  of  the  filtrate  taken  in  the  usual  man- 
ner. It  will  be  almost  always  decidedly  positive.  50  c.c.  of 
the  filtrate  are  inverted  as  described  on  page  124  and  the 
reading  again  taken  at  a  temperature  as  near  as  possible  to 
that  of  the  first  reading.  For  the  calculation  of  sucrose  see 
rules  on  page  125. 


326  FOOD    ANALYSIS 


ALCOHOLIC  BEVERAGES 

CIDER 

Cider  is  the  juice  of  apples  either  before  or  after  ferment- 
ing ;  when  the  alcohol  is  in  considerable  amount,  the  liquid  is 
often  called  "hard  cider."  Cider  differs  from  wine  in  con- 
taining no  tartrates,  and  larger  amounts  of  malates  and 
calcium  compounds.  Pear  cider,  often  called  "  perry," 
contains  more  sugar  than  apple  cider,  and  therefore,  yields 
more  alcohol  when  fully  fermented.  The  following  analyses 
of  apple  cider  by  R.  Kayser,  quoted  by  A.  H.  Allen,  represent 
the  same  sample  before  and  after  fermentation.  The  figures 
are  grams  per  100  c.c.: 

UNFER- 

MENTED.  FERMENTED. 

Total  solids, 16.25  2.36 

Alcohol, 4.6     (5. 8  c.c.) 

Ash,      0.35  0.31 

Malic  acid, 0.33  0.30 

Acetic  acid, .    .  0.08 

Sugar, 12.50  0.75 

Glycerol, 0.68 

G.  S.  Cox  obtained  the  following  results  from  unfermented 
cider  : 

Total  solids, 14.83     13.36 

Ash, ....    0.525     0.286 

Percentage  of  ash  to  solids,      .    . 3.54       2.14 

The  following  are  some  analyses,  by  J.  Embrey,  of  English 
and  American  ciders  : 

VOL.  ACID  FIXED  ACID 

ALCOHOL.  EXTRACT.  ASH.      SUGAR.  AS  ACETIC.  AS  MALIC. 
American  : 

I, 2.91            9.2         0.3         7.91  0.096  0.33 

2, 3.49           9.6         0.32       8.2  0.048  0.671 

3, 2.45           8.96       0.24       6.93  0.128  0.712 

English  : 

Unfermented  juice 

from  choice  apples,       0.2 1          1 2. 06         0.3     10.84  0.024  0.549 

New  English  cider,    .       3.32           6.7           0.34     3.86  0.144  0.244 

Old  English  perry,     .    .      3,64           4.5           0.3       0.36  0.222  0.244 


SPIRITS  327 

From  the  above  and  other  examinations  Embrey  is  of  the 
opinion  that  unwatered  cider  will  not  contain  less  than  0.25 
per  cent,  of  ash. 

ADULTERATIONS. — The  usual  adulterations  of  cider  are 
dilution  with  water,  addition  of  soda  or  lime  in  order  to  correct 
acidity,  and  addition  of  preservatives.  The  ash  of  cider  con- 
tains no  sodium.  When  heated,  it  volatilizes  at  a  compara- 
tively low  temperature,  and  imparts  to  flame  a  pure  potassium 
color.  The  dilution  of  cider  with  ordinary  water  containing 
even  a  small  proportion  of  sodium  may  be  detected  by  this 
test.  The  proportion  of  ash  to  the  original  solids  may  furnish 
some  indication  of  the  nature  of  a  sample  under  examination. 
In  unfermented  cider  the  proportion  of  ash  to  total  solids  will 
range  from  2  to  6  per  cent.  If  the  sample  be  fermented,  an 
allpwance  must  be  made  for  the  loss  in  solids.  (See  under 
"  Cider  Vinegar.") 

According  to  the  recommendations  made  to  the  A.  O.  A. 
C.  in  1897  by  the  referee  on  food  adulterations,  pure  cider 
will  have  the  following  composition  : 

GRAMS  PER  100  c.c. 

Alcohol, below  7 

Extract, 2.0    to  8.0 

Sugar, 0.4     to  4.0 

Total  acidity,  calc.  as  sulfuric  acid, 0.2    to  0.5 

Fixed  acids,  calc.  as  sulfuric  acid, o.  I    to  0.27 

Ash, 0.17  to  0.35 

Potassium  carbonate, 0.14100.23 

The  preservatives  used  are  commonly  salicylic  acid  and 
sulfites,  but  formaldehyde  is  now  sometimes  used.  The 
analysis  of  cider  is  to  be  conducted  according  to  the  methods 
given  for  alcoholic  beverages  proper. 


SPIRITS 

Spirits  are  the  liquors  obtained  by  the  distillation  of  alcoholic 
liquids.     The  latter  are  the  results  of  fermentation  of  saccha- 


328  FOOD    ANALYSIS 

rine  infusions  derived  from  barley,  oats,  wheat,  maize,  rice, 
potatoes,  or  from  the  juice  of  fruits,  sugar-cane,  beet-root,  etc. 
The  distilled  liquor  contains  water  and  ethyl  alcohol  along 
with  a  small  proportion  of  its  homologues  (fusel  oil),  aldehyde, 
acetic  acid,  and  various  esters.  The  amount  and  nature  of 
these  associated  bodies  will  depend  upon  the  nature  of  the 
fermented  material  and  the  method  of  manufacture.  The 
character  of  the  distilled  spirit  is  further  modified  by  the  addi- 
tion of  various  flavoring  materials. 


WHISKEY 

Whiskey  is  the  spirit  distilled  from  fermented  grain.  In 
some  cases  malted  grain  is  used,  but  more  usually  a  mixture 
of  malted  and  unmalted  grain  is  employed.  Spirit  from  raw 
grain  usually  contains  a  larger  proportion  of  fusel  oil.  The 
grain  commonly  employed  in  the  United  States  is  rye,  but 
wheat  and  maize  are  also  used  to  a  considerable  extent  and 
glucose  is  a  frequent  addition.  The  weak  spirit  (so-called 
"  low  wine  ")  which  is  obtained  by  distillation  is  usually  re- 
distilled, by  which  it  is  obtained  stronger  and  less  charged 
with  fusel  oil.  When  only  malted  grain  is  used,  the  liquid  is 
sometimes  distilled  in  small  stills,  called  "pot  heads,"  and  at 
once  set  aside  to  age  without  redistillation. 

Freshly  distilled  whiskey  is  colorless  and  of  disagreeable 
flavor.  It  is  usually  stored  in  sherry  casks,  where  it  is  allowed 
to  remain  for  a  considerable  time  until  it  has  aged  or  ripened, 
the  process  consisting  in  the  conversion  of  the  fusel  oil  into 
various  esters  of  agreeable  smell  and  taste.  At  the  same 
time  a  small  amount  of  tannin  and  other  matters  are  extracted 
from  the  cask,  and  the  whiskey  acquires  an  amber  or  yellow 
color,  which  is  frequently  heightened  by  the  addition  of  caramel, 
logwood,  catechu,  tea  infusions,  etc.  Old  whiskey  has  an 
acid  reaction,  due  to  the  presence  of  a  small  amount  of  acetic 


WHISKEY  329 

and  possibly  other  acids.     The  acidity  increases  with  age,  but 
is  rarely  over  o.  I  per  cent,  expressed  as  acetic  acid. 

The  U.  S.  Pharmacopeia  defines  whiskey  to  be  "a  distillate 
from  the  mash  of  fermented  grain,  as  maize,  wheat,  or  rye. 
It  is  an  amber-colored,  slightly  acid  liquid.  The  specific 
gravity  should  be  not  more  than  0.930  nor  less  than  0.917, 
corresponding  to  an  alcoholic  strength  of  from  44  to  50  per 
cent,  by  weight  or  50  to  58  per  cent,  by  volume.  If  100  c.c. 
be  slowly  evaporated  in  a  tared  capsule  in  a  steam-bath,  the 
last  portion  should  not  have  a  harsh  or  disagreeable  odor  (ab- 
sence of  more  than  mere  traces  of  fusel  oil.)  The  residue, 
dried  at  100°,  should  not  weigh  more  than  0.21  gram,  have 
no  sweet  or  distinctly  spicy  taste,  should  dissolve  almost  com- 
pletely in  10  c.c.  of  cold  water  to  form  a  solution  not  more 
deeply  colored  than  light  green  by  a  few  drops  of  ferric  chlorid 
solution  (absence  of  more  than  traces  of  oak  tannin).  100  c.c. 
of  whiskey  should  not  require  more  than  12  c.c.  ^  sodium  hy- 
droxid  to  render  it  distinctly  alkaline." 

In  Scotland  and  Ireland  the  drying  of  the  malt  takes  place 
in  kilns  in  which  peat  is  used  as  fuel,  and  the  spirit  whiskey 
made  from  it  has  a  strong  smoky  flavor.  This  is  often  im- 
itated by  the  addition  of  two  drops  of  creasote  to  the  gallon  of 
spirits.  A  variety  of  whiskey  is  sometimes  made  by  distilling 
cider,  and  is  known  as  apple-whiskey  or  apple-brandy. 

English  whiskies  are  occasionally  adulterated  with  methyl 
alcohol.  Cayenne  pepper  is  also  said  to  be  added  in  order  to 
give  greater  warmth  of  taste,  and  thus  enable  a  weak  spirit  to 
be  sold  for  a  strong  one.  In  some  cases  it  appears  to  have 
been  added  simply  as  a  flavor. 

Lead,  copper,  and  zinc  have  been  found  in  whiskey,  and  are 
probably  derived  from  the  apparatus  employed  in  the  dis- 
tillery. They  are  also  said  to  have  been  added  directly. 

The  following  are  some  results  of  analyses  of  commercial 
whiskey  by  A.  H.  Allen  : 


330  FOOD    ANALYSIS 


COMMERCIAL        COMMERCIAL 
SCOTCH  WHISKEY.  IRISH  WHISKEY. 


Specific  gravity, 0.9416  o. 

Alcohol  (percentage  by  weight), 39. 05  39-3° 

Secondary  constituents,  expressed  in  grains 
per  imp.  proof-gallon : 

Free  acid,  as  acetic, 10.2  6.8 

Ethers  in  terms  of  acetic  ether,      .    .    .    .  46.5  23.1 

Higher  alcohols  in  terms  of  amyl  alcohol,  89.6  78.8 

Aldehyde, Trace.  Trace. 

Furfural, "  " 


BRANDY 

Brandy,  also  called  French  brandy  or  "  cognac,"  is  the 
spirit  obtained  by  distilling  wine.  An  inferior  quality  is 
manufactured  from  skins  and  stalks  ("  marc  ")  of  the  grapes. 
Such  brandy  usually  contains  more  fusel  oil  than  that  made 
from  wine.  So-called  British  brandy  is  made  from  grain 
spirit  to  which  is  added  flavoring  esters,  such  as  ethyl  acetate, 
pelargonate  and  nitrate,  bitter  almonds,  spices,  and  caramel. 
Freshly  distilled  brandy  is  colorless,  but  on  standing  in  casks 
it  dissolves  a  minute  quantity  of  tannin  and  other  bodies  and 
acquires  an  amber  tint.  It  is  also  frequently  colored  with 
caramel. 

Ordonneau  obtained  the  following  results  from  a  French 
brandy,  25  years  old,  by  fractional  distillation  : 

GRAMS  PER  100  LITERS. 

Normal  propyl  alcohol, 40.0 

Normal  butyl  alcohol, 218.6 

Amyl  alcohol, ...     83.8 

Hexyl  alcohol, 0.6 

Heptyl  alcohol, 1.5 

Fthyl  acetate, 35.0 

Ethyl  propionate,  butyrate,  and  caproate, 3.0 

CEnanthic  ether, 4.0 

Aldehyde, 3.0 

The  ferment  of  grape  skins,  Sac  char  omyces  ellips  aides,  pro- 
duces normal  butyl  (tetryl)  alcohol,  but  in  fermentation  by 
brewer's  yeast  (S.  cerevisicz)  isobutyl  alcohol  is  formed.  By 


MALT    LIQUORS  33! 

the  use  of  the  former  ferment,  with  saccharine  solutions  other 
than  grape-juice,  a  spirit  may  be  produced  having  characters 
similar  to  French  brandy. 

GIN 

Gin,  and  the  varieties  known  as  Hollands  or  Schnapps,  are 
usually  prepared  by  redistilling  grain  spirit  which  has  been  fla- 
vored with  various  bodies,  among  which  may  be  mentioned 
juniper  berries  or  oil  of  juniper,  turpentine,  coriander  and  car- 
damon  seeds,  capsicum,  orris,  angelica,  and  calamus  roots. 
Gin  is  without  color  and  is  comparatively  free  from  fusel  oil 
and  the  associated  bodies  found  in  brandy  and  whiskey. 


RUM 

Rum  is  the  spirit  obtained  by  distilling  the  fermented  juice 
of  the  sugar-cane,  or,  more  commonly,  by  distilling  fermented 
molasses.  The  flavor  of  rum  is  due  largely  to  the  presence 
of  ethyl  butyrate  and  ethyl  formate.  It  is  colored  either  by 
long  keeping  in  casks,  or  by  the  addition  of  burnt  sugar. 
Much  of  the  commercial  article  is  made  from  grain  spirit  to 
which  has  been  added  butyric  acid  or  butyric  or  acetic  esters. 
Pineapple  and  tannin-containing  materials  are  also  added. 
According  to  A.  H.  Allen,  the  presence  of  formates  might 
serve  to  distinguish  genuine  rum  from  the  factitious  product. 
The  rum  should  be  evaporated  .almost  to  dryness  with  a 
slight  excess  of  sodium  hydroxid  and  the  residue  treated  with 
phosphoric  acid  and  distilled.  The  distillate  from  genuine 
rum  will  strongly  reduce  silver  nitrate,  and  give  the  other 
reactions  for  formic  acid. 

MALT  LIQUORS 

These  are,  strictly  speaking,  infusions  of  malt,  fermented 
by  yeast,  and  rendered  bitter  by  the  addition  of  hops.  Hop- 


332  FOOD    ANALYSIS 

substitutes  are  little  used  unless  the  price  of  hops  advances, 
when  quassia,  chiretta,  and  aloes  may  be  employed.  The 
common  substitutes  for  malt  are  unmalted  cereals,  glucose, 
and  starch. 

Two  methods  of  fermentation  are  in  use  for  the  prepara- 
tion of  beers.  The  "  high  "  or  "  surface  "  fermentation,  em- 
ployed for  English  beers,  takes  place  at  a  temperature  of  15° 
to  20°,  and  is  completed  in  from  4  to  8  days.  The  "low" 
or  "bottom"  fermentation,  employed  in  Germany,  takes 
place  at  a  temperature  of  from  4°  to  8°,  and  requires  from 
20  to  24  days  for  completion.  In  this  process  the  yeast 
remains  at  the  bottom  of  the  vat.  In  each  of  these  there  is 
a  predominance  of  particular  species  of  yeasts,  and  unless 
carefully  selected  and  cultivated,  the  yeast  mass  will  contain 
species  producing  irregular  and  often  objectionable  fermenta- 
tion-products. In  this  way  malt  liquors  may  acquire  unpleas- 
ant bitterness  or  odor,  or  troublesome  turbidity. 

The  following  are  the  principal  varieties  of  malt  liquors  : 

ALE,  made  from  a  light-colored  malt,  usually  with  addition 
of  glucose,  and  a  large  proportion  of  hops.  So-called  "mild 
ales "  are  usually  sweeter,  contain  a  larger  proportion  of 
alcohol,  and  are  less  bitter. 

PORTER  and  STOUT  are  principally  distinguished  from  the 
above  by  their  flavor,  derived  from  the  use  of  a  certain  pro- 
portion of  roasted  malt.  They  also  contain  less  hops. 

Ale,  porter,  and  stout  are  made  by  the  high  fermentation 
process.  LAGER  or  GERMAN  BEER  is  prepared  by  the  low 
fermentation  process  and  contains  less  alcohol,  more  sugar, 
dextrin,  and  nitrogeneous  matter,  and  is  more  highly  charged 
with  gas.  Lager  beers  are  liable  to  undergo  a  second  fer- 
mentation unless  kept  at  a  low  temperature. 

So-called  WEISSBIER  is  light-colored  and  about  half  the 
strength  of  lager  beer.  Rice  is  often  used  in  its  manufac- 
ture. 


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334  FOOD    ANALYSIS 

ROOT  BEERS  and  MEAD. — Solutions  of  cane-sugar  flavored 
with  herbs  and  roots  are  much  used  for  the  manufacture  of 
home-brewed  beers.  These  are  subjected  to  a  brief  fermenta- 
tion in  closed  vessels,  and,  as  a  rule,  but  insignificant  propor- 
tions of  alcohol  are  formed. 

The  principal  constituents  of  beer  are  as  follows  : 
Volatile. — Water,  alcohol,  acetic  and  other  acids. 

Fixed. — (Extract.)  Sugar,  chiefly  maltose,  dextrin,  and 
similar  bodies,  proteids,  glycerol,  lactic  acid,  succinic  acid, 
bitter  principles,  and  mineral  matters,  chiefly  phosphates. 

ADULTERATION. — The  chief  adulteration  of  malt  liquors 
consists  in  the  addition  of  substances  other  than  malt  and  of 
preservatives.  The  use  of  glucose  is  very  common,  and  may 
possibly  be  detected  by  the  presence  of  gallisin,  which  is  a 
usual  constituent  of  the  commercial  article.  The  substitu- 
tion of  any  considerable  proportion  of  glucose,  rice,  or  starch 
for  the  barley  will  be  indicated  by  the  lowered  proportion  of 
proteids,  ash,  and  phosphates. 

The  addition  of  preservatives,  especially  salicylic  acid, 
sodium  fluorid,  sodium  silicofluorid,  and  of  sulfites  is  very 
common.  Sodium  bicarbonate  is  also  added  in  order  to  cor- 
rect acidity.  The  quantity  of  chlorids  may,  at  times,  be  con- 
siderable, due  either  to  the  addition  of  salt,  or  to  the  presence 
of  chlorids  in  the  water  used  in  making  the  mash.  The  direct 
addition  of  salt  is  probably  infrequent. 

The  following  recommendations  as  to  standards  of  composi- 
tion of  beer  were  made  in  1897  to  the  Association  of  Official 
Agricultural  Chemists  by  the  referee  on  food  adulteration  : 

"  The  glycerol  content  of  beer  should  not  be  less  than  0.4 
gram  per  100  c.c.  The  ash  should  not  be  less  than  0.12  nor 
greater  than  0.30  gram  per  100  c.c.  The  presence  of  less 
than  o.  10  gram  indicates  that  some  malt  substitute  low  in  ash, 
such  as  starch,  has  been  used  in  the  preparation  of  the  beer, 
while  if  the  ash  content  be  greater  than  0.30  gram  per  100 


WINE  335 

c.c.,  and  the  volatile  acids,  calculated  to  acetic  acid,  less  than 
0.075  gram  per  100  c.c.,  it  is  probable  that  an  excess  of  acid 
has  been  neutralized  by  sodium  carbonate,  and  the  ash  of  the 
beer  should  be  examined  for  both  sodium  and  carbonic  acid. 
The  phosphoric  acid  should  not  be  less  than  0.05  gram  nor 
greater  than  o.  10  gram  per  100  c.c.  If  less  than  0.05  gram, 
it  is  probable  that  a  portion  of  the  malt  has  been  replaced  by 
starch  or  similar  substance." 


WINE 

Wine  has  been  defined  to  be  the  fermented  juice  of  the 
grape  with  such  additions  as  are  essential  to  the  stability  or 
keeping  of  the  liquid.  The  method  of  preparation  is,  briefly, 
as  follows  :  The  grapes  are  crushed,  the  stems  being  removed 
in  the  case  of  the  better  grades  of  wine,  and  the  juice  ex- 
pressed. The  juice  or  "must"  is  sometimes  allowed  to 
stand  in  contact  with  the  skins  for  several  days  in  order  to 
extract  additional  "bouquet."  In  the  case  of  red  wines,  the 
expression  of  the  juice  and  removal  of  the  skins  do  not 
take  place  until  the  fermentation  is  practically  completed. 
The  juice  of  most  varieties  of  grapes  are  colorless,  but  in  the 
presence  of  alcohol  formed  by  the  fermentation  the  red  color- 
ing-matter of  the  skin  is  extracted ;  red  wine  contains  a 
greater  proportion  of  tannin  than  white  wine.  The  chief  fer- 
mentation of  the  wine  usually  takes  place  in  from  four  days 
to  several  weeks,  according  to  the  temperature  at  which  it  is 
conducted.  After  this,  the  liquid  is  drawn  off  into  casks, 
where  a  secondary  quiet  fermentation  takes  place.  The  wine 
is  then  allowed  to  age  or  ripen,  a  process  which  involves 
chiefly  direct  oxidation,  and  during  which  potassium  acid  tar- 
trate  is  deposited,  along  with  a  considerable  proportion  of  the 
coloring-matter,  and,  by  the  interaction  of  the  alcohols  with 


336  FOOD    ANALYSIS 

the  acids   and  other  constituents   present,  various  esters  are 
formed  which  give  flavor  and  bouquet. 

The  yeast  that  ferments  the  must  is  found  on  grape  skins. 
There  are  many  varieties,  some  of  which  produce  special 
flavors,  and  by  the  application  of  these  in  special  cases  the 
flavor  of  the  wine  may  be  modified. 

Wines  prepared  as  above  usually  contain  very  little  sugar, 
and  are  termed  dry  wines,  as  distinguished  from  "  full- 
bodied  "  or  sweet  wines.  Some  wines  are  prepared  by  adding 
to  the  must  a  certain  proportion  of  alcohol,  which  causes  the 
fermentation  to  cease  before  the  complete  conversion  of  the 
sugar  is  effected.  Port  and  sherry  are  manufactured  in  this 
way. 

Champagne  is  usually  prepared  as  follows  :  The  pressed 
grapes  are  fermented  as  rapidly  as  possible  until  but  little 
sugar  is  left.  The  clarified  wine  is  blended  with  other  wine 
to  bring  it  to  the  quality  desired,  and  pure  sugar  (about  2  per 
cent.)  is  added  and  the  liquid  placed  in  strong  bottles,  which 
are  tightly  stoppered  and  placed  horizontally  until  fermenta- 
tion is  completed,  and  then  with  the  necks  downward,  and, 
as  the  wine  clarifies,  the  yeast-sediment  collects  on  the  stop- 
per. This  is  promoted  by  frequent  turning  and  manipula- 
tion of  the  bottle.  The  bottle  is  then  skilfully  uncorked  and 
a  small  portion  of  the  wine,  carrying  with  it  the  sediment, 
removed.  The  space  so  emptied  is  filled  by  the  addition  ot 
wine  and  a  certain  proportion  of  so-called  liqueur,  and  the 
bottle  recorked  and  wired.  These  operations  are  performed 
so  quickly  that  there  is  but  little  loss  of  carbon  dioxid.  The 
liqueur  consists  of  a  mixture  of  sugar,  wine,  and  cognac. 
Champagne  is  sometimes  prepared  by  adding  the  liqueur  to 
the  fermented  wine  and  charging  the  liquid  with  carbon  dioxid 
under  pressure. 

The  normal  constituents  of  wine  are  water,  alcohol  and  its 
homologues,  acetic  acid,  succinic  acid,  various  compound 


WINE  337 

ethers,  sugar,  gum,  pectin,  glycerol,  tannin,  coloring-matters 
(in  red  wine),  tartaric  acid,  calcium  or  potassium  tartrates, 
phosphates,  and  other  mineral  matter. 

The  sugar  in  wine  is  apt  to  be  chiefly  levulose,  dextrose 
being  more  readily  fermentable. 

The  table  on  page  338  gives  the  composition  of  must  and 
wines  'from  various  sources  expressed  in  grams  per  100  c.c. 
The  data  are  derived  in  most  cases  from  the  examination  of  a 
great  many  samples. 

ADULTERATION. — The  fact  that  the  composition  of  wine 
varies  within  notable  limits  renders  it  impossible  to  assign  ab- 
solute standards  and  allow  a  margin  for  the  addition  of  water 
and  other  substances  without  so  far  changing  the  composition 
as  to  enable  the  chemist  to  determine  whether  a  given  sample 
is  or  is  not  genuine.  Usually  it  can  only  be  stated  that  the 
satnple  conforms  in  composition  to  that  of  genuine  wine. 

In  some  cases  additions  to  the  wine  or  must  are  regarded 
as  legitimate.  Thus,  it  has  been  found  that  a  certain  propor- 
tion of  acid  to  sugar  in  the  must  is  best  adapted  to  the  pro- 
duction of  good  wine  ;  and  in  cases  in  which  this  proportion 
does  not  obtain,  it  is  the  practice,  in  some  localities,  to  make 
such  additions  as  are  necessary  to  bring  these  constituents 
within  the  proper  limits. 

The  following  conclusions  were  arrived  at  by  an  official 
German  commission  : 

The  total  extract  of  wines  should  not  be  below  1.5  grams 
per  100  c.c.  After  deducting  the  non-volatile  acids,  the  ex- 
tract should  be  at  least  i.i  grams  per  100  c.c. 

Natural  wines  usually  contain  a  close  approximation  of  I 
part  ash  to  10  parts  of  extract. 

The  proportion  of  free  acid  calculated  as  tartaric  acid  ap- 
pears not  to  exceed  one-sixth  of  the  total  volatile  acid. 

Genuine  wines  will  not  contain  less  than  0.14  gram  of  ash 
nor  more  than  0.05  gram  of  sodium  chlorid  in  100  c.c. 
29 


338 


FOOD    ANALYSIS 


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WINE  339 

The  following  recommendations  as  to  standards  were  made 
in  1897  to  the  A.  O.  A.  C.  by  the  referee  on  food  adultera- 
tion : 

"  The  composition  of  dry  wines  and  sweet  wines,  calcu- 
lated to  sugar- free  substances,  should  not  vary  far  from  the 
following  figures  : 

GRAMS  PER  100  c.c. 
Red.         White. 

Alcohol  (by  volume), 12.00  11.50 

Extract,  less  sugar, 2.80  2.00 

Total   acidity, 0.50  0.55 

Tannin  and  coloring-matter, 0.25  0.96 

Ash, 0.28  0.20 

These  figures  are  for  new  wines.  After  standing  for  two 
or  three  years  the  proportion  of  extract  will  decrease  about 
10  per  cent.  Wine  should  be  regarded  with  suspicion  which 
contain  less  than  2.4  grams  or  more  than  3.2  grams  of  ex- 
tract per  100  c.c.,  or  which  contain  less  than  0.2  gram  or 
more  than  0.35  gram  of  ash  per  100  c.c.,  or  if  the  total 
acidity  is  less  than  0.45  gram  hydrochloric  acid  per  100  c.c., 
the  ash  less  than  one-eighth  or  more  than  one-half  of  the 
sugar-free  extract,  the  sulfates  correspond  to  more  than  0.2 
gram  potassium  sulfate  per  100  c.c.,  and  thechlorin  calculated 
to  sodium  chlorid,  over  0.2  gram  per  100  c.c. 

"  With  American  wines  the  presence  of  volatile  acid,  calcu- 
lated to  acetic  acid,  in  excess  of  one-fourth  of  the  total  acid, 
may  be  considered  evidence  of  adulteration,  though  with 
European  wines  the  ratio  is  somewhat  larger." 

The  plastering  of  wines  consists  in  sprinkling  the  grape  or 
must  with  plaster-of- Paris,  with  a  view  of  securing  a  quicker 
fermentation,  better  color,  and  keeping  qualities.  Plastered 
wine  shows  but  a  small  increase  in  ash,  but  the  wine  from 
plastered  must  shows  a  large  increase  in  the  form  of  po- 
tassium sulfate  rather  than  calcium  sulfate.  If  a  wine  un- 
usually rich  in  sulfates  and  potassium  compounds  contains 


34O  FOOD    ANALYSIS 

little  or  no  tartar,  it  must  have  been  plastered,  and  the 
absence  of  alkalinity  in  the  ash  will  confirm  this. 

Sulfurous  acid  is  often  present  in  new  wines,  from  the  use  of 
sulfites  or  burning  sulfur  for  the  purpose  of  disinfecting  the 
casks. 

The  additions  to  wine  commonly  detected  are  sugar,  glu- 
cose, honey,  glycerol,  tartaric  acid  and  other  vegetable  acids, 
gums,  tannin,  vegetable  astringents,  coloring-matters,  flavor- 
ing ethers,  salicylic  acid  and  other  preservatives.  In  order  to 
increase  the  sugar,  total  extract  and  free  acid,  figs,  dates, 
tamarinds,  and  St.  John's  bread  are  frequently  employed. 
Dried  raisins  are  largely  used  for  the  manufacture  of  imita- 
tion wines. 

A  form  of  adulteration  is  the  decolorization  of  red  wine  by 
the  use  of  charcoal  or  possibly  potassium  permanganate,  the 
product  being  sold  as  a  genuine  white  wine.  H.  Astruc  has 
made  a  number  of  experiments  on  the  effect  of  decolorizing  by 
means  of  various  forms  of  charcoal,  including  crude  and  puri- 
fied bone-black,  lamp-blacks,  and  vegetable  charcoal.  All 
the  decolorizers  absorbed  a  little  alcohol  (0.4  to  1.5  per  cent, 
of  a  total  of  7.8)  ;  a  small  proportion  of  the  total  acidity  ;  0.5 
to  2.65  per  cent,  of  the  glycerol  (out  of  a  total  of  4.5  per 
cent.)  ;  and  0.95  to  2.65  per  cent,  out  of  a  total  of  3.45  per 
cent,  of  tannin,  besides  extracting  the  coloring-matter.  The 
crude  bone-blacks  are  distinguished  from  the  purified  blacks 
and  vegetable  charcoals  by  the  fact  that  they  remove  almost 
the  whole  of  the  tartrates  and  a  larger  proportion  of  glycerol, 
and  especially  double  the  proportion  of  mineral  matter  in 
solution,  the  increase  being  entirely  in  insoluble  ash  constit- 
uents (chiefly  calcium  phosphates),  whereas  the  soluble  por- 
tion is  diminished.  The  decolorizing  power  of  the  vegetable 
blacks  is  low  and  a  much  larger  quantity  is  required,  the 
effect  of  which  on  the  chemical  constitution  is  greater  than 
that  of  a  suitable  amount  of  bone-black. 


WINE  341 

The  following  is  an  analysis  by  Hougounenq  of  a  white 
wine  supposed  to  have  been  prepared  from  red  wine  by  the 
addition  of  potassium  permanganate  and  charcoal  : 

Alcohol, 7. 13  per  cent. 

Extract  (in  vacuo), 22.27  grams  per  liter. 

Ash, 3.59 

Alkalinity  of  ash  as  potassium  carbonate,    I.Io 

Potassium  sulfate, 1.14 

Acidity,  total,  as  sulfuric  acid,     ....  4.25 

"        volatile,  as  acetic  acid,    ....  1.23 

Reducing  substances  as  glucose,    .    .    .  1.47 

Glycerol, 1.07 

The  ash  was  red  and  porous.  The  sample  contained  0.59 
gram  of  manganous  oxid  per  liter. 

Analyses  of  pure  Ohio  wines  by  A.  W.  Smith  and  Norman 
Parks  are  of  interest  as  indicating  a  composition  in  some 
respects  different  from  European  wines.  The  average  of 
solids  is  slightly  lower  than  that  of  foreign  wines,  but  the 
most  important  differences  are  the  percentages  of  glycerol 
and  ash.  Published  reports  from  European  samples  give  ash 
usually  above  o.  I  per  cent.,  and  from  0.5  to  0.8  per  cent,  of 
glycerol,  while  the  maximum  and  minimum  found  with  the 
Ohio  samples  are  0.15  to  o.  10  for  ash,  and  0.95  and  0.29  for 
glycerol.  Since  these  two  constituents,  together  with  the 
solids,  are  of  much  value  in  determining  the  genuineness  and 
purity  of  a  sample  of  wine,  the  differences  are  most  important. 
Many  authorities  state  that  in  the  natural  process  of  alcoholic 
fermentation,  glycerol  and  alcohol  are  produced  in  the  ratio 
of  from  7  to  14  parts  of  the  former  to  100  parts  of  the  latter, 
from  which  would  be  drawn  the  inference,  when  this  maximum 
is  exceeded,  that  glycerol  had  been  added  ;  while  in  case  the 
ratio  of  glycerol  to  alcohol  is  below  7  :  100,  the  inference  would 
be  drawn  that  the  sample  has  been  fortified  by  the  addition 
of  alcohol.  Such  conclusions  in  the  case  of  Ohio  wines  would 
be  quite  misleading.  Smith  and  Parks  also  call  attention  to 
the  fact  that  care  must  be  exercised,  when  these  wines  are 


342  FOOD    ANALYSIS 

under  consideration,  in  drawing  conclusions  as  to  the  addition 
of  water  from  the  fact  of  low  ash  and  solids. 

Appreciable  amounts  of  copper,  zinc,  lead,  and  arsenic  are 
occasionally  found  in  wine.  These  are  probably  introduced 
along  with  crude  glucose,  anilin  colors,  or  other  materials 
which  have  been  added.  Lead  has  been  introduced  by  the 
use  of  bottles  that  have  been  cleaned  with  shot. 

ANALYTIC  METHODS. 

For  the  detection  of  alcohol  when  present  in  very  small 
amount  several  tests  have  been  devised,  but  the  reactions  are 
produced  by  other  substances.  The  following  are  the  most 
satisfactory.  They  should  be  applied  to  samples  containing 
no  active  ingredients  but  water  and  alcohol ;  ordinary  mix- 
tures should,  therefore,  be  distilled  and  the  distillate  tested. 

J.  Hardy's  Test. — A  small  quantity  of  powdered  guaiacum 
resin  taken  from  the  interior  of  a  lump  is  shaken  with  a  few 
c.c.  of  the  sample,  the  liquid  filtered,  and  a  few  drops  of  hy- 
drogen cyanid  solution  and  a  drop  of  very  dilute  copper  sul- 
fate  solution  added.  In  the  presence  of  alcohol  a  blue  tint 
much  deeper  than  that  due  to  the  copper  sulfate  will  appear. 

E.  Merck's  Modification  of  E.  W.  Davy's  Test. — Pure  mol- 
ybdenum trioxid  is  dissolved  in  warm  sulfuric  acid,  and  the 
mixture  poured  through  the  solution  to  be  tested,  keeping 
the  mess  as  nearly  as  possible  at  60°.  Alcohol  produces  a 
blue  ring  at  the  junction  of  the  liquids. 

Hager' s  Modification  of  Lieberis  Test. — 10  c.c.  of  the 
sample  are  mixed  with  5  drops  of  a  10  per  cent,  solution  of 
sodium  hydroxid  and  the  liquid  heated  to  about  50°.  Potas- 
sium iodid-iodin  solution  is  added  drop  by  drop  with  shaking 
until  the  liquid  is  permanently  yellowish-brown.  It  is  then 
decolorized  by  the  cautious  addition  of  more  sodium  hy- 
droxid. If  alcohol  is  present,  iodoform  will  be  produced 
as  a  yellow  precipitate  of  characteristic  odor  and  crystalline 


WINE  343 

form.  Under  rather  high  magnifying  power  (200  diameters) 
these  are  seen  to  consist  of  hexagonal  plates  or  six-pointed 
stars.  This  is  a  good  test,  but  requires  care.  The  iodin  so- 
lution should  be  strong  and  the  directions  should  be  followed 
closely.  The  reaction  is  given  by  many  bodies,  but  not  by 
methyl  alcohol,  fusel  oil,  common  ether,  chloral,  chloroform, 
or  glycerol. 

Specific  gravity  determinations  of  commercial  liquors  are 
occasionally  made,  but,  as  a  rule,  the  figures  have  little  prac- 
tical bearing. 

Alcohol  may  be  determined  directly  in  spirits  and  other 
mixtures  containing  but  little  solid  matter  by  taking  the 
specific  gravity  and  correcting  for  temperature.  This  is  the 
method  used  by  revenue  officers. 

For  determining  the  alcohol  in  samples  containing  appre- 
ciable amounts  of  solid  matters,  several  methods  have  been 
devised,  of  which  only  two  deserve  mention  here  :  distilla- 
tion and  observation  of  boiling-point. 

For  distillation  200  c.c.  of  the  sample  should  be  taken,  100 
c.c.  of  water  added,  the  mixture  distilled  until  200  c.c.  are 
collected.  The  specific  gravity  of  this  is  taken  at  standard 
temperature  and  the  percentage  of  alcohol  ascertained  by  the 
annexed  tables. 

The  following  tables  are  condensed  from  those  recalculated 
by  Edgar  Richards  from  the  determinations  of  Gilpin,  Drink- 
water  and  Squibb,  and  published  by  the  A.  O.  A.  C.  All  data 
are  given  at  —5.  The  figures  in  columns  designated  volume 
(V)  or  weight  (W)  are  percentages  of  absolute  alcohol,  by 
volume  or  weight  respectively,  corresponding  to  the  specific 
gravity  indicated.  When  the  percentage  in  two  lines  is  the 
same,  the  actual  difference  is  in  the  second  decimal  place, 
which  has  been  omitted  in  this  condensed  table  : 


344 


FOOD    ANALYSIS 


SPECI- 
FIC 
GRAV- 
ITY. 

VOL- 
UME. 

WEIGHT 

SPECI- 
FIC 
GRAV- 
ITY. 

VOL- 
UME 

WEIGHT 

SPECI- 
FIC 
GRAV- 
ITY. 

VOL- 
UME. 

WEIGHT 

SPECI- 
FIC 
GRAV- 
ITY. 

VOL- 
UME 

» 
WEIGHT 

1.  0000 

0.0 

0.0 

0.9928 

5-0 

4.0 

0.9866 

10.0 

8.0 

0.9811 

15-0 

12.  1 

0.9998 

i 

0 

26 

I 

0 

64 

I 

i 

IO 

I 

2 

96 

2 

I 

25 

2 

I 

63 

2 

2 

09 

2 

2 

95 

3 

2 

24 

3 

2 

62 

3 

2 

ON 

3 

3 

93 

4 

3 

22 

4 

3 

61 

4 

3 

07 

4 

4 

0.9992 

0-5 

0.4 

0.9921 

5-5 

4.4 

0.9860 

10.5 

8.4 

0.9806 

15-5 

12.5 

90 

6 

4 

20 

6 

4 

59 

6 

5 

05 

6 

6 

89 

7 

5 

18 

7 

5 

58 

7 

6 

04 

7 

7 

87 

8 

6 

17 

8 

6 

56 

8 

7 

03 

8 

7 

86 

9 

7 

16 

9 

7 

55 

9 

9 

02 

9 

8 

0.9984 

x.o 

0.7 

0.9914 

6.0 

4.8 

0.9854 

II.  0 

8.8 

0.9801 

16.0 

12.9 

83 

i 

8 

13 

i 

8 

53 

i 

9 

OO 

i 

13.0 

81 

2 

9 

12 

2 

9 

52 

2 

9.0 

0.9799 

2 

i 

80 

3 

I.O 

II 

3 

5-o 

5i 

3 

i 

98 

3 

2 

79 

4 

i 

09 

4 

i 

50 

4 

i 

97 

4 

2 

0.9977 

i-5 

i.i 

0.9908 

6-5 

5-2 

0.9849 

ii.  5 

9.2 

0.9796 

16.5 

13.3 

76 

6 

2 

07 

6 

2 

47 

6 

3 

95 

6 

4 

74 

7 

3 

05 

7 

3 

46 

7 

4 

94 

7 

5 

73 

8 

4 

04 

8 

4 

45 

8 

5 

92 

8 

6 

7i 

9 

5 

°3 

9 

5 

44 

9 

5 

9i 

9 

7 

0.9970 

2.0 

1-5 

0.9902 

7-o 

5-6 

0.9843 

12.0 

9.6 

0.9790 

17.0 

13-7 

68 

I 

6 

oo 

i 

6 

42 

I 

7 

89 

i 

8 

67 

2 

7 

0.9899 

2 

7 

4i 

2 

8 

88 

2 

9 

65 

3 

8 

98 

3 

8 

40 

3 

9 

87 

3 

14.0 

64 

4 

9 

97 

4 

9 

39 

4 

IO.O 

86 

4 

i 

0.9962 

2-5 

1.9 

0.9895 

7-5 

6.0 

0.9838 

12.5 

IO.O 

09785 

17-5 

14.1 

61 

6 

2.0 

94 

6 

i 

37 

6 

I 

84 

6 

2 

60 

7 

I 

93 

7 

i 

35 

7 

2 

83 

7 

3 

58 

8 

2 

92 

8 

2 

34 

8 

3 

82 

8 

4 

57 

9 

3 

90 

9 

3 

33 

9 

4 

81 

9 

5 

0-9955 

3-0 

2-3 

0.9889 

8.0 

6.4 

0.9832 

13-0 

10.4 

0.9780 

18.0 

14.6 

54 

i 

4 

88 

I 

5 

3i 

i 

5 

79 

I 

6 

52 

2 

5 

87 

2 

5 

30 

2 

6 

78 

2 

7 

5i 

3 

6 

86 

3 

6 

29 

3 

7 

77 

3 

8 

50 

4 

7 

84 

4 

7 

28 

4 

8 

76 

4 

9 

0.9948 

3-5 

2.8 

0.9883 

8-5 

6.8 

6.9827 

13-5 

10.9 

0-9775 

18.5 

15-0 

.47 

6 

8 

82 

6 

9 

26 

6 

9 

74 

6 

i 

45 

7 

9 

Si 

7 

9 

25 

7 

II.  O 

73 

7. 

i 

44 

8 

3-0 

80 

8 

7.0 

24 

8 

i 

72 

8 

2 

43 

9 

i 

78 

9 

i 

23 

9 

2 

7i 

9 

3 

0.9941 

4.0 

3-2 

0.9877 

1  9.0 

7.2 

0.9821 

14.0 

n-3 

0.9770 

19.0 

i5-4 

40 

i 

2 

76 

i 

3 

20 

i 

3 

69 

i 

5 

39 

2 

3 

75 

2 

3 

19 

2 

4 

68 

2 

5 

37 

3 

4 

74 

3 

4 

18 

3 

5 

67 

3 

6 

36 

4 

5 

73 

4 

5 

17 

4 

6 

66 

4 

7 

0.9934 

4-5 

3-6 

0.9871 

9-5 

7-6 

0.9816 

14-5 

11.7 

0.9765 

19-5 

15.8 

33 

6 

6 

70 

6 

7 

15 

6 

8 

64 

6 

9 

32 

7 

7 

69 

7 

8 

14 

7 

8 

63 

7 

16.0 

30 

8 

8 

68 

8 

8 

13 

8 

9 

62 

8 

0 

29 

9 

9 

67 

9 

9 

12 

9 

12.0 

61 

9 

i 

ANALYTIC    METHODS 


345 


S.  G. 

V. 

W. 

S.  G. 

V. 

w. 

S.  G. 

V. 

W. 

S.  G. 

V. 

W. 

0.9760 

20.0 

16.2 

0.9709 

25.0 

20.4 

0.9654 

30.0 

24.6 

0.9591 

35-0 

28.9 

59 

I 

3 

08    I 

5 

52 

I 

7 

89 

I 

29.0 

5* 

2 

4 

07   2     6 

51 

2 

8 

88 

2 

I 

57 

3 

5 

06 

3     6 

50 

3 

9 

86 

3 

2 

56 

4 

5 

05 

4     7 

49 

4 

25.0 

85 

4 

3 

0-9755  20.5 

16.6 

0.970425.5   20.8 

0.964830.5 

25.0 

0.958435.5 

29-3 

54 

6 

7 

03   6     9 

46   6 

82 

6 

4 

53 

7 

8 

02   7   21.0 

451   7 

2 

81 

7 

5 

52 

8 

9 

01 

8 

i 

441   8 

3 

80 

8 

6 

5i 

9   17.0 

oo   9 

i 

43   9 

4 

78 

9 

7 

0.9750 

21.0    17.0 

0.9699  26.0 

21.2 

0.9642  31.0 

25-5 

0-9577 

36.0 

29.8 

49 

I       I 

98 

I 

3 

40 

i 

6 

75 

i 

9 

48 

2       2 

96 

2 

4 

39 

2 

6 

74 

2 

30.0 

47 

3     3 

95 

3 

5 

38 

3 

7 

73 

3 

o 

•  46 

4     4 

94 

4 

6 

37 

4     8 

7i 

4 

i 

0.9745 

21-5    17.5 

0.9693  26.5 

21.6 

0.9636 

3i.5   25.9 

0.9570 

36.5 

30.2 

44 

6     5 

92 

6 

7 

34 

6 

26.0 

68 

6 

3 

43 

7     6 

91 

7 

8 

33 

7 

i 

67 

7 

4 

42 

8     7 

90 

8 

9 

32 

8 

2 

66 

8 

5 

4i 

9     » 

89   9 

22  O 

3i 

9 

2 

64 

9 

6 

0.9740 

22.  0    17.9 

0.9688  27.0 

22.1 

0.9629 

32.0   26.3 

09563 

37-o 

30.7 

39 

i   1  8.0 

87   i 

2 

28 

i 

4 

61 

i 

7 

38 

2       0 

86 

2 

2 

27 

2 

5 

60 

2 

8 

37 

3 

i 

85 

3 

3 

26 

3 

6 

58 

-: 

9 

3° 

4     2 

83 

4 

4 

24 

4 

7 

57 

4 

31.0 

0.9735 

22.5  18.3 

0.9682 

27-5 

22  .5 

0.9623  32.5   26.8 

0.9556 

37-5 

3i-i 

34 

6     4 

81 

6 

6 

22    6       8 

54 

6 

2 

33 

7 

5 

80 

7 

7 

21 

7 

9 

53 

7 

3 

32 

»     5 

79 

8 

7 

19 

8 

27.0 

51 

8 

4 

3i 

9     6 

7* 

9 

8 

18 

9 

i 

50 

9 

4 

0.973023.0   18.7 

0.9677  28.0 

22.9 

0.9617 

33-o 

27.2 

0.954838.0 

31-5 

29 

I] 

76 

i 

23-0 

15 

i 

3 

47 

i 

6 

28 

2 

9 

74 

2 

i 

14 

2 

4 

45 

2 

7 

27 

3 

ig.o 

73 

3 

2 

13 

3 

4 

44 

J 

8 

26   4     o 

72 

4 

j 

12   4 

5 

42 

4 

9 

0.972523-5   19-1 

0.9671 

28.5 

23-3 

0.961033.5   27.6 

0.9541 

38.5 

32.0 

24 

6       2 

70 

6 

4 

09 

;6 

7 

39 

6 

i 

23 

7     3 

69 

7 

5 

08 

7 

8 

38 

7 

2 

22 

8     4 

68!   8 

6 

06 

8 

q 

36 

1 

2 

21 

9     5 

66   9 

7 

05   9   28.0 

35 

( 

3 

0.9720 

24.0   19.5 

0.9665  29.0 

23-8 

0.960434.0 

28.0 

0-9533 

39-0 

32.4 

1C 

i 

6 

64   i 

8 

03 

i 

I 

32 

5 

i\ 

2 

63 

2 

9 

01 

2 

2 

30 

i 

6 

17 

3 

8 

62 

j 

24.0 

oc 

3 

29 

' 

7 

15 

4 

9 

61 

4 

i 

0.9599 

4 

4 

27   4 

8 

9.9714 

24.5    20.0 

0.9660  29.5 

24.2 

0.959734-5  28.5 

0.952639-5 

32.9 

13 

6     o 

5«   ^ 

3 

96   6     6 

24   6 

9 

12 

7     i 

57 

7 

t 

95   7 

23 

o 

11 

* 

2 

5^ 

8 

i 

93   * 

21 

i 

1C 

9     3 

55 

g 

5 

92 

S 

8 

2C 

c 

2 

30 


346 


FOOD    ANALYSIS 


S.  G. 

V. 

W. 

S.  G. 

V. 

W. 

S.  G. 

V. 

W. 

S.  G. 

v. 

W. 

0.9518 

40.0 

33-3 

0.9478 

42-5 

35-5 

0.9436 

45-o 

37-8 

0.9391 

47-5 

40.1 

16 

I 

4 

77 

6 

6 

34 

9 

89 

6 

2 

15 

2 

5 

75 

7 

7 

32 

2 

38.0 

87 

7 

3 

13 

3 

6 

73 

8 

8 

3i 

3 

i 

86 

8 

4 

12 

4 

7 

72 

9 

9 

29 

4 

2 

84 

9 

5 

0.9510 

40-5 

33-7 

0.9470 

43-o 

36.0 

0.9427 

45-5 

38.3 

0.9382 

48.0 

40.6 

09 

6 

8 

68 

i 

i 

25 

6 

3 

80 

i 

*6 

07 

7 

9 

67 

2 

2 

24 

7 

4 

78 

2 

7 

05 

8 

34-0 

65 

3 

3 

22 

8 

5 

76 

3 

8 

04 

9 

i 

63 

4 

3 

20 

9 

6 

74 

4 

9 

O.9502 

41.0 

34-2 

0.9462 

43-5 

36.4 

0.9418 

46.0 

38.7 

09373 

48.5 

41.0 

01 

i 

3 

60 

6 

5 

17 

I 

8 

7i 

6 

i 

0.9499 

2 

4 

58 

7 

6 

15 

2 

9 

69 

7 

2 

98 

3 

5 

57 

8 

7 

13 

3 

39-° 

67 

8 

3 

96 

4 

5 

55 

9 

8 

II 

4 

i 

65 

9 

4 

0-9494 

4i.5 

34-6 

0-9453 

44-o 

36.9 

0.9409 

46.5 

39-2 

0.9363 

49.0 

41-5 

93 

6 

7 

5' 

i 

37-o 

08 

6 

3 

61 

i 

£ 

9i 

7 

8 

5o 

2 

i 

06 

7 

3 

59 

2 

7 

90 

8 

9 

48 

3 

2 

04 

8 

4 

57 

3 

8 

88 

9 

35-0 

46 

4 

3 

O2 

9 

5 

55 

4 

9 

0.9486 

42.0 

35-i 

0.9445 

44-5 

37-3 

O.94OO 

47-0 

39-6 

0-9354 

49-5 

41.9 

85 

i 

2 

43 

6 

4 

0.9399 

i 

7 

52 

6 

42.0 

83 

2 

3 

4i 

7 

5 

97 

2 

8 

5o 

7 

i 

81 

3 

4 

39 

8 

6 

95 

3 

9 

48 

8 

2 

80 

4 

4 

38 

9 

7 

93 

4 

40.0 

46 

9 

3 

Alcohol  may  be  determined  by  noting  the  temperature  of 
the  vapor  from  the  boiling  liquid.  Wiley  has  described  a 
form  of  apparatus  (Fig.  52)  for  this  purpose.  It  consists  of 
the  flask,  F,  which  is  closed  by  the  rubber  stopper,  carrying 
the  large  thermometer,  B,  and  a  tube  leading  to  the  con- 
denser, D.  The  vapors  which  are  given  off  during  ebullition 
are  condensed  in  D  and  return  to  the  flask  through  the  tube, 
as  indicated  in  the  figure,  entering  the  flask  below  the  surface 
of  the  liquid. 

The  flask  is  heated  by  a  gas-lamp  and  is  placed  upon  a  per- 
forated disk  of  asbestos  in  such  a  way  as  to  entirely  cover  the 
hole  in  the  center  of  the  asbestos  disk,  which  is  a  little 
smaller  than  the  bottom  of  the  flask.  The  whole  apparatus 
is  protected  from  external  influences  of  temperature  by  the 


ANALYTIC    METHODS 


347 


glass  cylinder,  E,  which  rests  upon  the  asbestos  disk  below 
and  is  covered  with  a  detachable,  stiff  rubber-cloth  disk  above. 

The  thermometer,  C,  indicates  the  temperature  of  the  air 
between  F  and  E.  The 
reading  of  the  thermom- 
eter, B,  should  always 
be  made  at  a  given  tem- 
perature of  this  sur- 
rounding air.  The  tube 
leading  from  the  con- 
denser, D,  to  the  left  is 
made  long  and  is  left 
open  at  its  lower  ex- 
tremity in  order  to  main- 
tain atmospheric  pres- 
sure in  F  and  at  the 
same  time  prevent  the 
diffusion  of  the  alcoholic 
vapors  through  D. 

The  flame  of  the  lamp 
is  so  regulated  as  to 
bring  the  temperature  in- 
dicated by  the  thermom- 
eter C  to  about  90°  in 
ten  minutes,  for  sub- 
stances containing  not 
over  5  per  cent,  of  alco- 
hol. After  boiling  for  a 
few  minutes,  the  tern-  FlG 

perature,  as  indicated  in 

the  thermometer  B,  is  constant,  and  the  readings  of  the  ther- 
mometer should  be  made  at  intervals  of  about  half  a  minute, 
for  ten  minutes.  Some  pieces  of  scrap  platinum  placed  in 
the  flask  will  prevent  bumping  and  secure  a  more  uniform 


348  FOOD    ANALYSIS 

evolution  of  vapor.  Slight  variations,  due  to  the  changes 
in  temperature  of  the  vapors,  are  thus  reduced  to  a  minimum 
effect  upon  the  final  results.  The  apparatus  is  easily  oper- 
ated, is  quickly  charged  and  discharged,  and  with  it  at  least 
three  determinations  of  alcohol  can  be  made  in  an  hour. 

The  thermometer  used  is  the  same  that  is  employed  for  the 
freezing  and  boiling  points  in  the  determination  of  molecular 
weights.  The  reading  of  the  thermometer  is  arbitrary,  but 
the  degrees  indicated  are  centigrade.  The  thermometer  is  set 
in  the  first  place  by  putting  the  bulb  in  water  containing  16 
grams  of  common  salt  to  100  c.c.;  when  the  water  is  fully 
boiling,  the  excess  of  mercury  is  removed  from  the  column  in 
the  receptacle  at  the  top,  and  then,  on  placing  in  boiling 
water,  the  column  of  mercury  will  be  found  a  little  above  the 
5°  mark.  This  will  allow  a  variation  in  all  of  5°  in  the  tem- 
perature, and  a  thermometer  thus  set  can  be  used  for  the  esti- 
mation of  percentages  of  alcohol  from  one  to  five  and  a  half, 
by  volume.  When  the  liquor  contains  a  larger  percentage  of 
alcohol  than  this,  it  is  advisable  to  dilute  it  until  it  reaches  the 
limit. 

In  order  to  avoid  frequent  checking  of  the  thermometer, 
rendered  necessary  by  changes  in  barometric  pressure,  a 
second  apparatus,  made  exactly  like  the  one  described,  is 
used,  in  which  water  is  kept  constantly  boiling.  It  is  only 
necessary,  in  this  case,  to  read  the  two  thermometers  at  the 
same  instant,  in  order  to  make  the  necessary  correction  re- 
quired by  changes  in  barometric  pressure. 

Each  0.8°  corresponds  to  about  I  per  cent,  by  volume  of 
alcohol  in  liquors  containing  not  more  than  5.5  per  cent. 
For  example,  if,  in  a  given  case,  the  temperature  of  the  vapor 
of  boiling  water,  as  marked  by  the  thermometer,  is  5.155° 
and  the  temperature  of  that  from  a  sample  of  beer  is  2.345°, 
the  difference  is  equivalent  to  2.810°,  and  the  percentage  of 
alcohol  by  volume  is,  therefore,  2.81  divided  by  0.80  =  3.51. 


ANALYTIC    METHODS  349 

The  thermometer  used  is  graduated  to  hundredths  of  a 
degree,  and  may  be  read  by  a  cathetometer  to  0.005°. 

The  thermometer  is  protected  and  its  reading  facilitated  by 
covering  the  bulb  with  a  test-tube  containing  water. 

Extract  is  determined  as  indicated  on  page  36.  When  the 
amount  exceeds  6  per  cent,  it  will  be  best  to  dilute  the 
sample  with  an  equal  volume  of  water,  making  allowance  for 
this  in  calculating  results.  Some  operators  advise  the  use  of 
50  c.c.  for  this  determination,  but  it  is  likely  that  equally 
good  results  can  be  obtained  in  small  dishes  with  10  c.c. 

Ask.  —  The  residue  from  the  extract  determination  is  incin- 
erated at  as  low  a  heat  as  possible.  Repeated  moistening, 
drying,  and  heating  to  redness  are  advisable  to  get  rid  of  car- 
bon. 

"Gum  and  Dextrin  (in  wine).  —  4  c.c.  of  the  sample  are 
mixed  with  10  c.c.  of  96  per  cent,  alcohol.  If  gum  arabic  or 
dextrin  is  present,  a  lumpy,  thick,  and  stringy  precipitate  is 
produced  ;  pure  wine  becomes  at  first  opalescent  and  then 
gives  a  flocculent  precipitate. 

Total  Acidity.  —  Any  carbonic  acid  present  is  removed  by 
shaking  a  portion  of  the  sample  ;  25  c.c.  are  transferred  to  a 
beaker  and,  with  white  wines,  10  drops  of  neutral  litmus 
solution  added.  Decinormal  sodium  hydroxid  solution  is 
added  until  the  red  color  changes  to  violet,  and  then  in  small 
amounts  until  a  drop  of  the  liquid  placed  on  delicate  red  lit- 
mus-paper shows  an  alkaline  reaction.  The  result  is  ex- 
pressed in  terms  of  tartaric  acid  : 

I  c.c.  _5L  sodium  hydroxid  solution  =  0.0075  gram  tartaric  acid. 


Determination  of  Volatile  Acids.  —  50  c.c.  of  wine  to  which  a 
little  tannin  has  been  added,  to  prevent  foaming,  are  distilled 
in  a  current  of  steam.  The  flask  is  heated  until  the  liquid 
boils,  the  lamp  turned  down,  and  the  steam  passed  through 


FOOD    ANALYSIS 

until  200  c.c.  have  been  collected  in  the  receiver.  The  dis- 
tillate is  titrated  with  ™  sodium  hydroxid  solution,  and  the 
result  expressed  as  acetic  acid  : 

I  c.c.     N    sodium  hydroxid  solution  =  0.006  gram  acetic  acid. 

10 

Total  Sulfites. — 25  c.c.  of  normal  potassium  hydroxid  are 
placed  in  a  200  c.c.  flask,  50  c.c.  of  the  sample  added,  best 
by  means  of  a  pipet,  the  liquids  mixed  and  allowed  to  stand 
15  minutes  with  occasional  shaking.  10  c.c.  of  dilute  (25 
percent.)  sulfuricacid  are  added,  with  3  c.c.  of  starch  solution, 
and  the  mixture  titrated  with  --  iodin  solution  introduced  as 

10 

rapidly  as  possible.  The  number  of  c.c.  of  iodin  required  to 
secure  a- blue  color  lasting  for  some  minutes,  multiplied  by 
0.00128,  will  give  the  equivalent  of  sulfurous  acid  in  grams  per 
100  c.c.  The  sulfurous  acid  existing  as  such  is  estimated  by 
treating  50  c.c.  of  the  sample  in  a  200  c.c.  flask  with  5  c.c.  of 
the  dilute  sulfuric  acid,  adding  a  small  piece  of  sodium  carbonate 
to  expel  air,  and  titrating  with  ^  iodin  as  before,  using  the  same 
multiplier  to  obtain  grams  per  100  c.c. 

Glycerol. — 100  c.c.  of  wine  are  evaporated  in  a  porcelain 
dish  to  about  loc.c.,  I  gram  of  quartz  sand  and  2  grams  of 
milk  of  lime  containing  40  per  cent,  calcium  hydroxid  added, 
and  the  evaporation  cautiously  carried  almost  to  dryness. 
The  residue  is  mixed  with  50  c.c.  of  alcohol,  90  per  cent,  by 
weight,  using  a  glass  pestle  or  spatula  to  break  up  any  solid 
particles,  heated  just  to  boiling  on  the  water-bath,  allowed  to 
settle,  and  the  liquid  filtered  into  a  flask  graduated  at  100  and 
110  c.c.  The  residue  is  repeatedly  extracted  in  a  similar 
manner  with  10  c.c.  portions  of  hot  alcohol.  The  contents 
of  the  flask  are  cooled  to  15°,  diluted  with  alcohol  to  the 
100  c.c.  mark,  and  filtered  rapidly.  50  c.c.  of  the  filtrate 
are  evaporated  to  a  sirup  in  a  porcelain  dish  on  hot,  but  not 
boiling  water,  the  residue  transferred  to  a  small  glass-stop- 


ANALYTIC    METHODS  351 

pered  graduated  cylinder,  with  the  aid  of  20  c.c.  absolute 
alcohol,  and  three  portions  of  20  c.c.  of  pure  ether  added, 
shaking"  well  between  each  addition.  The  mixture  is  allowed 

o 

to  stand  until  clear,  decanted  through  a  filter,  the  cylinder 
washed  at  least  three  times  with  a  mixture  of  I  part  abso- 
lute alcohol  and  1.5  parts  of  pure  ether,  the  washings  being 
added  to  the  filtrate.  The  latter  is  evaporated  to  a  sirup, 
dried  for  one  hour  at  100°,  and  weighed.  The  weight 
doubled  gives  the  grams  of  glycerol  per  100  c.c.  of  sample. 

Artificial  Colors. — Arata's  wool-test  (page  77)  will  serve  in 
many  cases.  The  following  additional  tests  are  taken  from 
publications  of  the  A.  O.  A.  C.  : 

0.2  gram  of  precipitated  mercuric  oxid  are  added  to  loc.c. 
of  the  sample,  the  mixture  shaken  for  one  minute,  and  filtered. 
Natural  colors  give  a  colorless  or  light  yellow  filtrate.  A  fil- 
trate showing  a  red  tint  indicates  that  an  artificial  color  is 
present. 

200  c.c.  of  wine  are  freed  from  alcohol  by  concentration, 
2  to  4  c.c.  of  10  per  cent,  hydrochloric  acid  added,  and  some 
threads  of  fat-free  wool  immersed  and  boiled  for  five  minutes. 
The  threads  are  removed,  washed  with  cold  water,  acidified 
with  hydrochloric  acid,  then  with  hot  water  similarly  acidified, 
then  with  pure  water.  The  coloring-matter  is  dissolved  from 
the  threads  by  immersion  in  a  boiling  mixture  of  50  c.c.  water 
and  2  c.c.  of  strong  ammonium  hydroxid.  This  liquid  is 
then  acidified  with  hydrochloric  acid,  new  threads  immersed 
and  boiled  for  five  minutes.  It  is  stated  that  in  the  presence 
of  artificial  colors  to  an  amount  of  0.002  gram  per  1000  c.c. 
the  threads  are  affected  as  follows  : 

Safranin,      light  rose-red. 

Bordeaux  red, rose-red  to  violet. 

Ponceau  red, rose-red. 

Fuchsin, dirty  white. 

Tropeolin  GO, straw  yellow. 

Tropeolin  OOO, light  orange. 

Corallin, dirty  white. 


352  FOOD    ANALYSIS 

Special  method  for  fuchsin  and  archil  :  20  c.c.  of  wine  are 
mixed  with  10  c.c.  of  lead  acetate  solution,  heated  slightly, 
well  mixed,  filtered,  2  c.c.  of  fusel  oil  added,  and  the  mixture 
shaken.  If  the  fusel  oil  be  colored  red,  it  is  removed  and 
divided  into  two  portions.  To  one  portion  hydrochloric  acid 
is  added  ;  to  the  other,  ammonium  hydroxid.  If  fuchsin  was 
present,  the  liquor  will  be  decolorized  in  both 
cases,  but  with  archil  the  ammonium  hydroxid 
will  produce  a  purple  violet. 

An  extraction  method  for  detecting  caramel  or 
prune  juice  in  spirits  has  been  devised  by  Crampton 
and  Simons  : 

50  c.c.  of  the  sample  are  evaporated  on  the 
water-bath  nearly  to  dryness,  the  residue  washed 
into  a  50  c.c.  flask,  25  c.c.  of  absolute  alcohol 
added,  and  the  solution,  after  cooling  to  standard 
temperature,  made  up  to  the  50  c.c.  mark  and 
mixed.  25  c.c.  are  transferred  to  a  separating  ap- 
paratus and  agitated  with  50  c.c.  of  ether  at  inter- 
vals for  about  thirty  minutes.  When  the  layers 
are  separated,  the  watery  layer  is  diluted  to  25  c.c., 
the  contents  of  the  flask  are  shaken,  and  the  liquids 
again  allowed  to  separate.  The  water-layer  will 
be  increased  slightly,  and  25  c.c.  of  it  should  be 
FIG  <  drawn  off  for  comparison  with  the  25  c.c.  of  solu- 
tion which  has  not  been  treated  with  ether.  By 
comparing  the  two  liquids  in  a  tintometer,  quantitative  obser- 
vations may  be  made.  The  coloring-matter  of  oak-wood  is 
soluble  in  ether,  and,  therefore,  spirits  not  artificially  colored 
become  lighter  when  treated  by  this  method. 

Crampton  and  Simons  advise  the  use  of  Bramwell's  modi- 
fication of  Rose's  apparatus  for  the  operation.  It  is  shown 
in  figure  53.  The  upper  bulb  should  have  a  capacity  of 
about  150  c.c.;  the  lower  bulb  should  have  a  capacity  of  25 


ANALYTIC    METHODS  353 

c.c.,  including  a  portion  of  the  connecting  stem.  This  stem 
should  have  a  caliber  about  4  mm.  and  it  is  graduated  in 
0.02  c.c.  from  20  c.c.  to  25  c.c.,  the  upper  mark  only  being 
shown  in  the  figure.  For  diluting  the  watery  layer  as  di- 
rected in  the  process,  it  is  best  to  attach  a  rubber  tube  to 
the  lower  opening  and  connect  the  other  end  of  the  rubber 
tube  to  a  flask  of  water.  By  elevating  the  flask  and  con- 
trolling the  flow  of  water  by  the  stopcock,  any  amount  of 
liquid  may  be  introduced. 

Fusel  Oil. — Of  the  many  processes  devised  for  this  deter- 
mination, the  following  is  selected.  It  is  transcribed  as  given 
in  the  Bulletin  of  the  A.  O.  A.  C.  The  separator  (Fig.  53) 
is  used  ;  the  reagents  are  : 

Alcohol  free  from  fusel  oil  prepared  by  fractional  distillation 
over  sodium  hydroxid  and  diluted  so  as  to  contain  exactly 
30  per  cent,  of  absolute  alcohol  by  volume  (sp.  gr.,  0.96541 
at  15.6°). 

Anhydrous  chloroform  redistilled. 

Diluted  sulfur ic  acid  (sp.  gr.,  1.2857  at  I5-6°)- 

To  dilute  any  sample  of  alcohol  to  a  given  percentage  mix 
a  volumes  of  the  alcohol  with  sufficient  water  to  make  b  vol- 
umes of  the  product,  a  being  the  volume-percentage  desired 
and  b  the  volume-percentage  of  the  original  liquid.  Allow 
the  mixture  to  stand  until  full  contraction  has  occurred  and 
the  original  temperature  reached  and  make  up  any  deficiency 
with  water.  For  example,  if  it  be  desired  to  dilute  a  distil- 
late containing  50  per  cent,  of  alcohol  by  volume  until  it 
contains  30  per  cent.  :  30  volumes  of  the  50  per  cent,  alco- 
hol are  mixed  with  enough  water  to  make  50  volumes. 

Analytic  operation :  200  c.c.  of.  the  sample  are  distilled 
until  about  25  are  left,  the  flask  is  allowed  to  cool,  25  c.c. 
of  water  added  to  the  contents,  and  distilled  again  until  the 
total  distillate  measures  200  c.c.  The  volume-percentage  of 


354  FOOD    ANALYSIS 

this  is  ascertained  and  it  is  diluted  to  30  per  cent,  by  the  rule 
above  given. 

The  special  tube  and  separate  flasks  containing  sufficient  of 
the  various  reagents  and  the  properly  diluted  distillate  are  im- 
mersed in  water  at  1 5°  until  all  have  attained  that  temperature. 
The  tube  should  have  a  rubber  cap  over  the  lower  end  to 
prevent  entrance  of  water.  When  the  temperature  is  reached, 
the  tube  is  filled  to  the  20  c.c.  mark  with  chloroform, 
drawing  it  through  the  lower  end  by  suction  ;  then  100  c.c. 
of  the  purified  alcohol  are  added  and  I  c.c.  of  the  diluted 
sulfuric  acid,  the  apparatus  inverted,  and  shaken  vigorously 
for  3  minutes.  The  stopcock  should  be  opened  a  couple  of 
times  to  equalize  pressure.  The  tube  is  placed  for  15  minutes 
in  water  at  15°,  turning  occasionally  to  hasten  the  separation 
of  the  reagents,  and  then  the  volume  of  .the  chloroform 
noted.  After  thoroughly  cleansing  and  drying  the  apparatus, 
the  operation  is  repeated,  using  the  diluted  distillate  from  the 
sample  under  examination,  in  place  of  the  purified  alcohol. 
The  increase  in  the  chloroform  volume  with  the  sample  under 
examination  over  that  with  the  standard  alcohol  is  due  to  fusel 
oil,  and  this  difference  (expressed  in  c.c.),  multiplied  by 
0.663,  gives  the  volume  of  fusel  oil  in  100  c.c.,  which  is  equal 
to  the  percentage  of  fusel  oil  by  volume  in  the  30  per  cent, 
distillate.  This  must  be  calculated  to  the  percentage  of  fusel 
oil  by  volume  in  the  original  liquor. 

Gallisin  and  Foreign  Bitters. — For  the  detection  of  gallisin, 
indicating  the  use  of  commercial  glucose,  the  following  method, 
due  to  Haarstick,  is  recommended  :  I  liter  of  the  beer  is 
evaporated  to  a  thin  sirup,  and  300  c.c.  of  90  per  cent,  alco- 
hol gradually  added  in  quantities  of  I  to  2  c.c.,  and  finally  95 
per  cent,  alcohol  until  the  filtrate  does  not  give  the  slightest 
turbidity  with  95  per  cent,  alcohol.  The  liquid  is  filtered 
after  standing  for  twelve  hours,  most  of  the  alcohol  distilled 
off,  and  the  remainder  evaporated.  The  residue  is  dissolved 


ANALYTIC    METHODS 


355 


in  water,  diluted  to  1000  c.c.,  and  fermented  at  20°  with  well- 
washed  beer  yeast.  After  two  or  three  days  a  little  fresh 
yeast  is  added,  and  on  the  fourth  day  fermentation  is  complete. 
The  concentrated  liquor  will  show  no  dextrorotation  if  no  gal- 
lisin  was  present. 

The  following  outline  process  for  the  detection  of  foreign 
bitter  principles  in  beer  is  due  to  A.  H.  Allen  :  3  7 


1000  c.c.  are  evaporated  half  and  precipitated  boiling  with  lead  acetate,  the  liquid  boiled 
for  fifteen  minutes  and  filtered  hot.  If  any  precipitate  occur  on  cooling,  the  liquid  is 
again  filtered. 


PRECIPITATE 
contains  hof>- 
bitter,  c  ar  a- 

FILTRATE.    The  excess  of  lead  is  removed  by  hydrogen  sulfid,  and  the 
filtered  liquid  concentrated  to  about  150  c.c.  and  tasted.     If  bitter,  the 
liquid  is  slightly  acidulated  with  dilute  sulfuric  acid,  and  shaken  re- 

mel- bitter, 

peatedly  with  chloroform. 

op  he  lie    acid 

(from       chir- 

etta),  phos- 
phates,  albu- 

CHLOROFORM   LAYER,    on 
evaporation,  leaves  a  bit- 

AQUEOUS LIQUID  is  shaken  with  ether. 

minous    mat- 

ter extract  in  the  case  of 

ters,  etc. 

gentian,   calumba,    quas- 

ETHEREAL  LAYER  leaves 

AQUEOUS  LI- 

1      sta.  and    old  hops  (only 

a  bitter  residue  in  the 

QUID,       if 

slightly  or  doubtfully  bit- 
ter in  the  case  of  chiretta).     The  residue  is 

case   of    chiretta,  gen- 
tian, or  calumba.     It  is 

still  bitter, 
is  rendered 

dissolved    in    a    little    alcohol,   hot  .water 

dissolved  iir  a  little  al- 

alkaline 

added,  and  the   hot   solution   treated  with 

cohol,  hot  water  added, 

and 

ammoniacal  basic  lead  acetate  and  filtered. 

and    the    hot    solution 

shaken 

treated    with    ammoni- 

with ether- 

acal  basic  lead  acetate 

c  hlor  o- 

PRECIPITATE    contains    old 

FILTRATE     is 

and  filtered. 

form.        A 

hops,  gentian,  and  traces 

boiled  to  re- 

bitter    ex- 

of caramel  products.     It  is 

move  ammo- 

tract    may 

suspended    in    water,   de- 
composed    by    hydrogen 
sulfid,    and    the    solution 

nia,        a  n  d 
treated  with 
a   slight  ex- 

P R  E  C  I  P  I- 
TATE       is 

treated 

FILTRATE 
is  treated 
wilh        a 

be    due   to 

berberin 
(calumba) 

agitated  with  chloroform. 

cess  of  sul- 

with 

slight  ex- 

or    strych- 

furic acid,  fil- 

water 

cessof  di- 

nin. 

tered      and 

and      de- 

lute   sul- 

CHLOROFORM 

AQUEOUS 

tasted.        I  f 

composed 

fnric 

LAYER  is  ex- 
amined     by 
special  tests 
for     gentian 
and  old  hop- 
bitter. 

LIQUID 

contains 
traces  of 
caramel- 
bitter. 

bitter,    it    is 
agitated 
with  chloro- 
form,     and 
the     residue 
examined 
for    calumba 

by  hydro- 
gen    sul- 
fid.    The 
filtered 
liquid    is 
bitter   in 
presence 

acid,    fil- 
tered and 
tasted. 
Bitter- 
ness indi- 
cates cal- 
umba   or 

The  aqueous 
liquid, 
separated 
from       the 
ether-chlo- 
roform , 

and  quassia. 

of     gen- 
tian. 

chiretta, 
which 

may  c  on- 
tain  cara- 
mel-bitter 

may       be 
re-ex- 

or cholin. 

tracted 

with  ether 

and      fur- 

ther    ex- 

amined. 

^=* 

or 


356  FOOD    ANALYSIS 

Methyl  Alcohol, — Crude  methyl  alcohol  is  sometimes  added 
to  ethyl  alcohol  to  unfit  it  for  use  as  a  beverage.  This  prac- 
tice is  not  followed  in  the  United  States,  but  the  invention  of 
methods  for  refining  methyl  alcohol  by  which  a  nearly  pure 
article  is  produced,  has  led  to  its  use  in  adulterating  ethyl 
alcohol  and  alcoholic  beverages.  S.  P.  Mulliken  and  H. 
Scudder  have  devised  the  following  test. 

If  the  sample  be  a  concentrated  spirit,  it  should  be  diluted 
three  or  four  times  before  taking  a  portion  for  test.  When 
various  organic  bodies  are  present,  as  in  malt  liquors  and 
tinctures,  the  sample  should  be  distilled  and  the  portion  pass- 
ing over  between  50°  and  100°  collected.  This  distillate 
should  give  a  clear  colorless  solution  when  shaken  with 
water.  In  some  cases,  as  when  acids  or  phenolic  bodies  are 
present,  it  will  be  advisable  to  add  sodium  hydroxid  before 
distilling. 

A  close  spiral  of  about  2  cm.  long  is  made  by  winding 
light  copper  wire  around  a  lead-pencil.  The  metal  is  super- 
ficially oxidized  by  heating  in  the  upper  part  of  a  burner 
flame,  and  while  red  hot  plunged  in  3  c.c.  of  the  sample, 
diluted,  if  necessary,  as  above.  The  treatment  is  repeated  at 
least  once  ;  if  the  percentage  of  methyl  alcohol  is  supposed 
to  be  small,  the  treatment  should  be  repeated  several  times, 
cooling  the  liquid  between  each  immersion.  One  drop  of  0.5 
per  cent,  aqueous  solution  of  resorcinol  is  added  and  the 
mixture  poured  cautiously  upon  strong  sulfuric  acid.  A 
rose-red  zone  will  be  promptly  developed  if  methyl  alcohol 
was  originally  present.  The  hot  wire  converts  the  methyl 
alcohol  into  formaldehyde,  which  gives  the  color.  Care  must 
be  taken  not  to  use  much  resorcinol.  If  much  ethyl  alde- 
hyde be  present  in  the  sample,  it  will  be  of  advantage  to  boil 
the  liquid,  after  the  hot  wire  treatment,  in  a  flask  attached  to 
an  inverted  condenser,  as  ethyl  aldehyde  evaporates  more 
readily  under  these  conditions  than  formaldehyde.  It  is  also 


ANALYTIC    METHODS  357 

well  to  make  a  blank  test  with  the  resorcinol  solution,  sulfuric 
acid,  and  the  untreated  sample  to  determine  if  any  bodies  are 
present  that  simulate  or  mask  the  color  reaction. 

Polarimetric  Examination. — In  the  routine  examination  of 
wine  polarimetric  readings  are  taken  directly  (after  clarifica- 
tion, if  necessary).  Sweet  wines  are  examined  directly,  also 
after  inversion  and  fermentation.  The  following  are  the  direc- 
tions for  these  processes  given  by  the  A.  O.  A.  C.  : 

Clarification. — For  white  wines,  60  c.c.  of  the  sample 
are  mixed  with  3  c.c.  of  lead  subacetate  solution  and  3  c.c. 
of  water  and  filtered.  33  c.c.  of  the  filtrate  are  mixed  with 
1.5  c.c.  of  a  saturated  solution  of  sodium  carbonate  and  1.5  c.c. 
of  water,  again  filtered,  and  examined  in  the  polarimeter. 
The  reading  must  be  multiplied  by  1.2  to  compensate  for  the 
dilution.  For  red  wines  the  same  amount  of  sample  is  taken, 
and  6  c.c.  of  lead  subacetate  solution  are  used  without  addi- 
tion of  water.  33  c.c.  of  the  filtrate  are  treated  with  3  c.c. 
saturated  sodium  carbonate  solution,  filtered,  and  the  reading 
multiplied  by  1.2.  With  sweet  wines  100  c.c.  are  mixed  with 
2  c.c.  of  lead  subacetate  solution  and  8  c.c.  of  water  and  fil- 
tered. 55  c.c.  of  the  filtrate  are  mixed  with  0.5  c.c.  of  satu- 
rated sodium  carbonate  solution  and  4.5  c.c.  of  water,  filtered, 
and  the  reading  multiplied  by  1.2  ;  33  c.c.  of  the  filtrate,  prior 
to  the  addition  of  the  sodium  carbonate,  are  mixed  with  3  c.c. 
of  hydrochloric  acid  and  the  liquid  inverted  according  to  the 
method  on  page  1 24.  The  liquid  is  cooled  quickly,  filtered,  the 
reading  taken  at  known  temperature,  and  multiplied  by  1.2. 
50  c.c.  of  the  sample  are  freed  from  alcohol  by  concentration, 
made  up  to  the  original  volume  with  water,  mixed  with  some 
well-washed  beer  yeast,  and  the  mass  kept  at  30°  until  fer- 
mentation is  complete,  which  will  usually  require  from  48  to 
72  hours.  The  liquid  is  then  transferred  to  100  c.c.  flask,  a 
few  drops  of  acid  mercuric  nitrate  added  (p.  213),  then  some 
lead  subacetate  solution,  followed  by  the  saturated  sodium 


358  FOOD   ANALYSIS 

carbonate  solution.     The  flask  is  filled  to  the  mark,  the  liquid 
mixed,  filtered,  and  the  reading  multiplied  by  2. 

The  polarimetric  data  obtained  in  the  above  examinations 
are  interpreted  according  to  the  following  schedule  : 

If  the  direct  examination  shows  no  rotation,  the  sample  may 
nevertheless  contain  invert-sugar  associated  with  the  dextro- 
rotatory unfermentable  impurities  of  glucose  or  with  sucrose. 
If  inversion  results  in  a  levorotation,  sucrose  was  present.  If 
fermentation  results  in  dextrorotation,  it  shows  that  invert- 
sugar  (or  some  other  levorotatory  fermentable  carbohydrate) 
and  the  unfermentable  constituents  of  glucose  were  present. 
If  the  inversion  or  fermentation  produces  no  change,  sucrose, 
unfermentable  constituents  of  glucose,  and  levorotatory  sugars 
are  absent. 

If  the  direct  examination  shows  dextrorotation,  sucrose  and 
the  unfermentable  constituents  of  glucose  may  be  present. 
If  after  inversion  it  is  levorotatory,  sucrose  was  present ;  if 
dextrorotatory  to  more  than  2.3  divisions  of  the  sugar  scale, 
the  unfermentable  impurities  of  glucose  were  present ;  if  the 
dextrorotation  is  less  than  2.3  divisions  and  more  than  0.9,  a 
portion  of  the  original  specimen  must  be  submitted  to  the 
following  treatment:  210  c.c.  are  mixed  with  o.i  gram  of 
potassium  acetate  and  evaporated  to  a  thin  sirup,  which  is 
mixed  with  200  c.c.  of  90  per  cent,  alcohol,  with  constant 
stirring,  the  solution  is  filtered,  the  alcohol  removed  by  distil- 
lation until  about  5  c.c.  remain,  the  residue  is  mixed  with 
washed  bone-black,  filtered  into  a  graduated  cylinder,' and 
washed  until  the  filtrate  amounts  to  30  c.c.  If  this  filtrate 
shows  a  dextrorotation  of  more  than  1.5  divisions  on  the 
sugar  scale,  the  impurities  of  glucose  were  present. 

If  the  direct  examination,  shows  levorotation,  and  this  is 
increased  by  inversion,  sucrose  and  levorotatory  sugar  were 
present.  If  the  sample  after  fermentation  shows  levorotation 
of  3  divisions,  it  contains  only  levorotatory  sugars.  If  after 


MALT-EXTRACTS  359 

fermentation  it  rotates  to  the  right,  levorotatory  sugars  and 
the  unfermentable  impurities  of  glucose  were  present. 

MALT-EXTRACTS 

Some  commercial  malt-extracts  are  semi-solid  mixtures  of 
diastase  with  hydrolyzed  starch,  /.  e.,  maltose,  dextrose,  and 
dextrin.  No  alcohol  is  present ;  preservatives  and  coloring- 
matters  are  not  likely  to  be  used.  Other  extracts  are  dark- 
colored  liquids,  containing  from  3  to  7  per  cent,  of  alcohol,  5 
to  15  per  cent,  of  solids,  mostly  organic,  but  little,  if  any, 
active  diastase.  Preservatives  are  liable  to  be  used  in  this 
class,  salicylic  acid  being  the  most  common. 

The  usual  examination  of  malt-extracts  will  involve  detec- 
tion of  preservatives  (page  86),  determination  of  alcohol,  solid 
matter,  and  diastatic  power.  Qualitative  tests  for  diastase 
may  be  made  as  follows  :  50  c.c.  of  a  solution  of  5  grams 
arrowroot  starch  in  looo  c.c.  of  water  are  mixed  with  I  gram 
of  the  extract  to  be  tested,  and  the  mixture  heated  in  a 
water-bath  within  the  limits  of  35°  and  45°.  Every  few 
minutes  a  drop  of  the  liquid  is  tested  on  a  porcelain  plate 
with  a  drop  of  iodin  solution  (page  35),  until  the  blue  color 
ceases  to  appear.  It  is  not  worth  while  to  continue  the  ex- 
periment beyond  a  half  hour,  as  a  malt-extract  that  will  not 
transform  the  starch  in  that  time  is  of  little  value.  The  solu- 
tion should  not  be  acid.  This  method  is  of  no  value  for 
quantitative  measurement.  For  such  purpose,  it  is  necessary 
to  estimate  the  reducing  sugar  formed  in  presence  of  a  large 
amount  of  starch.  10  grams  of  arrowroot  starch  are  stirred 
into  about  100  c.c.  of  cold  water,  the  mixture  added,  with 
constant  stirring,  to  250  c.c.  of  boiling  water,  and  the  boiling 
continued  until  the  starch  is  well  diffused  through  the  mass. 
The  solution  is  diluted  to  500  c.c.  when  cold.  50  c.c.  of  this 
solution  are  mixed  with  0.5  gram  of  the  sample  and  the  mix- 
ture kept  at  a  temperature  between  35°  and  45°  for  half  an 


360 


FOOD    ANALYSIS 


hour.  The  reducing  sugar  is  measured  by  the  volumetric 
method  described  on  page  1 16,  care  being  taken  that  the  liquid 
is  sufficiently  diluted.  An  experiment  without  addition  of 
starch  must  be  made  to  determine  the  amount  of  reducing 
substance  in  the  extract. 

In  some  cases  rough  comparative  approximations  may  be 
made  by  comparing  the  color  produced  by  iodin  at  the  end  of 
the  heating,  but  the  liquid  must  be  largely  diluted,  and  the 
indications  are  merely  suggestive. 


FLESH-FOODS 

Descriptions  of  anatomic  and  histologic  characters  of  flesh- 
foods  need  not  be  given  here.  The  following  table,  from  data 
compiled  by  A.  H.  Allen,  will  show  the  principal  constituents 
of  meats  from  different  classes  of  animals.  The  figures  are 
percentages  ;  they  must  be  regarded  as  approximations,  as  the 
analytic  processes  are  still  imperfect : 

MEAT  FROM  :                                 WATER.  PROTEID.  FAT.  ASH. 

Ox  (lean), 76.7  20.7  1.5  .2 

Ox  (fat), 55.4  17.1  26.3  .1 

Mutton, 76.0  17.1  5.7  .3 

Mutton  (fat),       .    .     ....       48.0  14.8  36.4  0.8 

Pig,      72.6  19.9  6.2  .1 

Horse, 74.3  21  6  2.5  .o 

Hare, 74.1  23.3  .1  .1 

Deer,    .    , 75.7  19.7  .9  .1 

Chicken,      76.2  19.7  .4  .3 

Pigeon, 75.1  22.1  .o  .o 

Lobster, 76.6  19.1  .1  .1 

Oyster, 80.3  14.1  .5  •    .7 

Herring,      74.6  14.5  9.0  .7 

Mackerel, 71.2  19.4  8.0  .3 

Salmon, 64.3  21.6  12.7  .3 

Cod, 82.2  1 6. 2  0.3  .3 

ANALYTIC  METHODS. 

Water. — 5  grams  of  the  finely  divided  material  are  dried 
according  to  the  methods  described  on  pages  37—41,  Parsons' 
method  being  especially  worth  trial  in  this  connection. 


FLESH-FOODS  361 

As/i. — The  dry  residue  obtained  in  the  water  determina- 
tion is  incinerated  according  to  the  methods  given  on  pages 

47-49- 

Total  Nitrogen. — The  Kjeldahl-Gunning  process  is  em- 
ployed. The  nitrogen,  multiplied  by  6.25,  will  give  an 
approximation  to  the  proteids  present.  If  nitrates  are  present, 
as  will  be  the  case  with  some  preserved  meats,  the  modified 
process,  page  45,  must  be  used. 

Fat. — Much  of  the  fat  in  meat-samples  can  be  removed  by 
mechanical  methods,  but  some  adheres  obstinately  to  the 
muscle-tissue,  and  it  is  probable  that  errors  have  been  made 
in  this  respect,  as  with  condensed  milk.  It  has  been  suggested 
that  the  muscle-tissue  be  digested  with  pepsin  and  hydro- 
chloric acid  and  the  fat  extracted  from  the  mass.  Good 
results  have  been  claimed  for  the  following  process  :  2  grams 
of  the  material  are  shaken  frequently  for  six  hours  with  200 
c.c.  of  ether  and  2  c.c.  of  mercury  and  the  fat  determined  in 
an  aliquot  part  of  the  mixture. 

Most  investigators  use  too  much  material.  It  is  probable 
that  results  near  enough  for  practical  purposes  could  be 
obtained  by  continuous  extraction  for  some  hours  of  a  few 
grams  of  the  material,  but  care  should  be  taken  that  the 
sample  represents  a  fair  average  of  the  specimen  and  that  it  is 
very  finely  divided  without  loss  of  fat.  If  the  fat  is  to  be 
examined,  a  large  amount  of  it  should  be  extracted  by 
mechanical  means,  and  not  with  solvents,  unless  there  are 
special  reasons  to  the  contrary. 

Adulteration. — Meats  are  not  adulterated  in  the  sense  in 
which  that  word  is  commonly  used,  but  cheap  meats  are  sub- 
stituted for  dear  (e.  g.,  horse  meat  in  sausages  and  mince- 
meat), the  meat  of  diseased  and  immature  animals  is  often 
sold,  preservatives  are  employed,  and  applications  made  to 
improve  color  or  texture.  The  detection  of  entozoa  is  a 
matter  of  importance.  Tests  for  incipient  and  actual  decom- 


362  FOOD    ANALYSIS 

position  may  be  required.  A  large  amount  of  canned  meat 
is  now  sold.  Much  of  it  is  free  from  adulteration. 

Horseflesh. — The  detection  of  horseflesh  is  difficult.  Many 
processes  have  been  proposed,  but  they  are  all  open  to  objec- 
tion. The  principal  reliance  is  upon  the  detection  of  glycogen, 
which  is  present  in  horseflesh  in  much  greater  proportion  than 
in  most  other  flesh.  The  following  process,  by  Courlay  and 
Coremons,  seems  to  be  the  most  trustworthy  :  50  grams  of 
the  material,  as  fresh  as  possible,  are  finely  divided  and  boiled 
for  thirty  minutes  with  200  c.c.  of  water.  The  liquid  is  filtered 
when  cold  and  tested  with  a  few  drops  of  potassium  iodid- 
iodin  solution  (page  35).  A  brown  tint,  disappearing  at  80° 
and  returning  on  cooling,  indicates  horseflesh.  If  starch  be 
present,  the  original  broth  should  be  treated  with  several 
times  its  measure  of  strong  acetic  acid,  and  the  test  applied 
to  the  filtrate.  The  above  test  has  been  modified  by  T.  Bas- 
tien,  by  increasing  the  time  of  boiling  to  one  hour  and  allow- 
ing the  liquid  to  concentrate  to  one-third  of  its  original  bulk. 
The  quantity  of  iodin  solution  should  be  quite  small,  in  which 
case  it  is  said  that  horseflesh  will  give  only  a  transient  reddish- 
violet.  The  strength  of  the  acetic  acid  is  not  given  in  the 
report  of  the  method. 

H.  Bremer  states  that  the  most  definite  test  for  horseflesh 
is  the  character  of  the  intramuscular  fat.  For  this  test,  all 
visible  fat  is  removed  from  a  sample,  the  mass  finely  minced, 
and  heated  in  water  for  an  hour  at  100°.  The  fat  that  floats 
is  poured  off  with  the  water,  the  flesh  washed  several  'times 
with  boiling  water,  dried  for  twelve  hours  at  100°,  and  the 
material  then  extracted  for  several  hours  with  petroleum 
spirit  of  low  boiling-point.  Part  of  the  fat  thus  obtained  may 
be  set  aside  for  the  determination  of  iodin  number,  but  most 
of  it  should  be  saponified,  the  excess  of  alkali  carefully  neu- 
tralized with  acetic  acid,  and  any  alcohol  that  may  have  been 
used  in  the  saponification  removed  by  evaporation  on  the 


FLESH-FOODS  363 

water-bath.  The  glycerol-soda  method  would  seem  to  be 
applicable  here.  The  soap  is  dissolved  in  water,  a  hot  solu- 
tion of  zinc  acetate  added  in  the  proportion  of  I  part  of  the 
salt  to  2  of  fat,  the  precipitate  washed  with  hot  water  and 
alcohol,  pressed  between  folds  of  filter-paper,  and  heated  with 
ten  times  its  volume  of  anhydrous  ether  for  thirty  minutes 
under  a  reflux  condenser.  The  solution  is  cooled,  filtered 
into  a  separating  funnel,  mixed  with  dilute  hydrochloric  acid, 
the  ethereal  layer,  which  contains  the  acids,  washed  with 
water,  and  parts  of  it  filtered  into  weighed  flasks,  the  ether 
evaporated,  and  the  iodin  number  determined. 

It  is  stated  that  horseflesh  always  gives  a  reddish- brown 
tint  to  the  petroleum  spirit  solution,  but  bull's  flesh  also  gives 
such  a  tint.  If,  however,  glycogen  has  been  detected  by 
the  tests  already  mentioned,  the  petroleum  spirit  solution  is 
reddish-brown,  the  iodin  number  of  the  fat  exceeds  65  and 
that  of  the  liquid  acids,  obtained  as  above,  is  considerably 
over  95,  the  presence  of  horseflesh  may  be  inferred. 

Coloring-matter. — Meats  are  not  infrequently  colored  to 
give  them  a  fresh  look  or  to  improve  naturally  pale  samples. 
Sausage  meats  are  often  colored.  Carmine  and  coal-tar 
colors,  especially  the  latter,  are  often  employed.  Fuchsin 
and  eosin  are  among  these,  but  Allen  states  that  benzo- 
purpurin  is  the  most  common.  The  detection  of  artificial 
colors  will  generally  be  accomplished  satisfactorily  by  the  test 
on  page  77.  E.  Spath  has  found  that  heating  the  material 
for  a  short  time  on  the  water-bath  with  a  5  per  cent,  solu- 
tion of  sodium  salicylate  will  often  dissolve  out  colors  not 
otherwise  soluble.  Ordinarily,  water  or  alcohol  will  take  out 
sufficient  for  the  wool-test.  For  the  detection  of  carmine, 
the  method  of  Klinger  and  Bujard,  modified  by  Bremer, 
should  be  used  :  20  grams  of  the  minced  material  are  heated 
for  several  hours  with  a  mixture  of  equal  parts  of  glycerol 
and  water  slightly  acidulated  with  tartaric  acid.  The  yellow 


364  FOOD    ANALYSIS 

liquid  is  freed  from  fat,  filtered,  and  the  coloring-matter  pre- 
cipitated as  a  lake  by  the  addition  of  alum  and  ammonium 
hydroxid.  This  is  washed,  dissolved  in  a  little  tartaric  acid, 
and  examined  in  the  spectroscope.  Absorption  bands  lying 
between  the  position  of  b  and  D  of  the  solar  spectrum  are 
characteristic  of  carmine. 

Improvers  and  Preservatives. — Mixtures  of  potassium  ni- 
trate, sodium  chlorid,  and  other  mineral  preservatives  with  a 
little  coloring-matter — the  latter  almost  always  a  coal-tar 
color — are  sold  for  improving  the  appearance  of  meat.  Sali- 
cylic acid,  boric  acid,  and  sulfites  are  also  apt  to  be  used,  and 
should  be  sought  for  according  to  the  methods  given  on  pages 
86  to  91.  As  they  are  all  soluble  in  cold  water,  they  may 
be  extracted  by  simple  maceration,  the  watery  solution  being 
concentrated  at  a  low  temperature  and  treated  as  directed  at 
the  above  reference.  Formaldehyde  is  not  likely  to  be  used 
in  meat  on  account  of  its  hardening  action  on  proteids. 

Putrefaction. — To  detect  incipient  putrefaction,  Ebers  pro- 
posed the  following  test :  A  rod  moistened  with  a  mixture  of 
hydrochloric  acid  I  c.c.,  alcohol  3  c.c.,  and  ether  I  c.c.  is 
held  over  the  suspected  material.  The  formation  of  fumes  of 
ammonium  chlorid  shows  that  putrefaction  has  begun.  Care 
must  be  taken  not  to  mistake  the  fumes  of  the  hydrochloric 
acid  for  those  of  ammonium  chlorid. 

It  has  been  proposed  to  detect  putrefaction  by  macerating 
the  finely  divided  material  in  water,  cautiously  distilling  the 
liquid,  best  probably  in  a  current  of  steam,  and  testing  the 
distillate  for  phenol.  The  reactions  noted  on  page  91  would 
probably  be  useful.  In  the  early  stages  of  decay  phosphor- 
escent microbes  are  sometimes  developed  which  render  the 
meat  luminous  in  the  dark,  but  this  is  not  common. 

Diseased  and  Immature  Meats. — The  detection  of  these 
conditions  are  questions  of  pathology  and  veterinary  medi- 
cine. Ebers  attempted  to  devise  a  scheme  for  the  detection 


FLESH-FOODS  365 

and  estimation  of  the  hydrogen  sulfid  evolved  by  diseased 
meat,  but  the  work  did  not  pass  beyond  the  experimental 
stage. 

Infected  Meats. — The  lower  animals  are  subject  to  para- 
sitic diseases  communicable  to  human  beings.  The  most 
important  are  two  species  of  so-called  tapeworm  and  the 
Trichina  spiralis.  One  species  of  tapeworm,  Tcenia  saginata, 
is  found  in  one  stage  of  development  in  beef;  another  species, 
7.  solium,  is  found  in  pork.  This  condition  is  often  termed 
"  measles."  Trichina  spiralis  is  principally  found  in  pork. 
Many  other  animal  parasites  are  known,  but  recognition  of 
them  belongs  to  pathology  and  biology. 

Tcenia  saginata  Goeze,  also  called  T.  mediocannellata,  occurs 
in  beef  as  little  white  cysts  among  the  muscular  fibers,  like 
knots  in  wood.  The  mature  animal  is  developed  from  the 
cysts  when  the  meat  is  eaten.  It  is  the  common  tapeworm 
of  the  United  States. 

Tcenia  solium  L.  occurs  in  the  flesh  of  the  hog.  It  differs 
from  7.  saginata  in  the  important  fact  that  the  latter  can  not 
pass  through  all  its  stages  of  development  in  the  same  ani- 
mal, while  T.  solium  can  extend  its  infection  to  various 
organs  of  the  host. 

Trichina  spiralis  Owen  is  a  worm  that  occurs  in -hog-flesh 
as  light-colored  cysts,  smaller  than  a  pin's  head,  and  usually 
lying  with  the  long  diameter  in  the  direction  of  the  muscular 
fiber.  The  cysts  contain  immature  worms,  which  are  released 
when  the  cyst  is  digested  ;  the  worm  quickly  reaches  matur- 
ity, muliplies  rapidly,  and  distributes  itself  through  various 
tissues  of  the  host. 

The  detection  of  the  various  parasites  of  meat  can  often  be 
attained  by  examining  with  a  good  hand-glass.  With  higher 
powers,  the  organism  can  be  seen  in  more  detail. 

Canned    Meats. — These  are  now   usually  prepared  on  a 


366  FOOD    ANALYSIS 

very  large  scale  at  establishments  under  inspection  and  hence 
are  but  little  liable  to  adulteration.  Preservatives,  except 
common  salt  and  niter,  are  not  likely  to  be  employed.  If  any 
other  preservative  should  be  used  it  will  probably  be  boric  acid 
or  possibly  salicylic  acid,  either  of  which  can  be  easily  detected 
in  the  extract  with  cold  water  by  methods  given  elsewhere. 
Tin  and  sometimes  lead  are  absorbed  in  small  amounts  from 
the  can  or  solder.  These  may  be  tested  for  by  the  methods 
given  on  page  69.  Careful  examination  under  moderate 
magnifying  power  will  detect  parasitic  infection. 

Meat-extracts. — These  are  now  offered  in  great  variety. 
Some  contain  partly  digested  proteids  (proteoses  and  peptones), 
but  in  many  cases  the  most  abundant  nitrogenous  ingredients 
are  the  so-called  meat-bases,  a  class  of  amido-derivatives  of 
which  kreatin,  kreatinin,  and  xanthin  are  examples. 

Many  investigations  of  these  preparations  have  been  made, 
but  the  processes  of  analysis  are  still  in  dispute  and  the 
results  obtained  by  different  observers  are  often  discordant. 
The  following  methods  are  compiled  from  the  works  of 
A.  H.  Allen  38  and  C.  A.  Mitchell.39 

Water,  Ash,  and  Total  Nitrogen  are  determined  as  indicated 
under  those  titles  in  the  introductory  part. 

Fat  is  usually  present  in  but  small  amount,  and  is  extracted 
more  accurately  by  petroleum  spirit  than  by  ether,  applying 
the  methods  described  on  pages  49  to  53. 

Insoluble  matter,  which  may  include  some  meat-fiber,  is 
determined  by  treating  from  5  to  25  grams  (depending  on 
whether  the  preparation  is  solid  or  liquid)  with  cold  water, 
filtering,  and  drying  the  residue  at  100°.  A  microscopic 
examination  of  this  should  be  made. 

Proteids,  Peptones,  and  Meat-bases.  The  following  method 
has  been  suggested  by  A.  H.  Allen,  partly  from  his  own 
experiments  and  partly  from  those  of  A.  Bomer : 


FLESH-FOODS  367 

50  c.c.  of  a  solution  of  a  known  weight  of  the  sample,  of 
such  strength  as  to  contain  about  1.5  grams  of  nitrogenous 
bodies,  are  freed  from  insoluble  material,  mixed  with  I  c.c.  of 
diluted  sulfuric  acid  (i  to  4),  and  saturated  with  zinc  sulfate 
by  stirring  in  the  powdered  salt  until  no  more  dissolves.  Zinc 
sulfate  containing  the  full  amount  of  water  of  crystallization 
dissolves  in  about  half  its  weight  of  water  at  room  tempera-, 
ture,  but  the  commercial  salt  is  usually  partly  effloresced,  and 
will  often  cake  when  added  to  the  solution.  When  the  liquid 
is  saturated  with  zinc  sulfate,  the  precipitate  is  assumed  to 
contain  all  the  albumin  and  gelatin  and  immediate  derivatives 
(proteoses),  but  no  peptone.  It  is  separated  by  filtration, 
washed  with  a  saturated  solution  of  zinc  sulfate,  and  the  filter 
and  precipitate  treated  by  the  Kjeldahl-Gunning  method.  The 
nitrogen  obtained,  multiplied  by  6.25,  will  give  approximately 
the 'amount  of  nitrogenous  bodies  precipitated. 

The  filtrate  and  washings  are  made  up  to  200  c.c.,  mixed, 
and  100  c.c.  transferred  to  a  flask  of  the  larger  form  described 
on  page  42,  enough  hydrochloric  acid  added  to  make  the  liquid 
strongly  acid  to  litmus,  and  then  bromin  water  by  moderate 
portions,  with  active  shaking  or  stirring,  until  there  is  an 
excess  of  bromin  present.  The  precipitate  may  be  flocculent 
at  first,  but  most  of  it  soon  becomes  viscous  and  adherent.  It 
is  allowed  to  stand  until  the  free  portions  have  settled,  when 
it  is  decanted  through  an  asbestos  filter  either  in  a  Gooch  cru- 
cible or  in  an  apparatus  similar  to  that  described  on  page  120. 
The  precipitate  is  washed  several  times  with  cold  water  con- 
taining some  hydrochloric  acid  and  bromin,  but  it  is  advisable 
to  keep  the  washings  at  first  separate  from  the  main  filtrate. 
The  contents  of  the  filter-tube  are  returned  to  the  vessel  in 
which  the  precipitation  was  made,  10  c.c.  of  sulfuric  acid 
added,  and  the  mass  cautiously  treated  until  it  chars  and 
vapors  of  bromin  are  evolved,  after  which  10  grams  of  potas- 
sium sulfate  are  added  and  the  operation  conducted  as 


368  FOOD    ANALYSIS 

described  on  pages  44  and  45.  The  nitrogen,  multiplied  by 
6.33,  will  give  approximately  the  peptone. 

By  deducting  from  the  total  nitrogen  the  sum  of  the  nitro- 
gen figures  obtained  from  the  zinc  sulfate  and  bromin  precipi- 
tates, and  multiplying  the  remainder  by  3.12,  an  approxima- 
tion to  the  meat-bases  will  be  obtained.  These  meat-bases 
are  in  the  filtrate  from  the  bromin  precipitate,  but  the  bromin, 
hydrochloric  acid,  and  zinc  sulfate  will  be  likely  to  interfere 
with  the  determination  of  the  nitrogen.  The  zinc  sulfate  can 
be  removed  by  cautious  addition  of  either  potassium  carbon- 
ate or  barium  hydroxid,  but  the  bromin  will  be  apt  to  form 
hypobromites,  which  will  promptly  decompose  some  of  the 
amido-compounds,  with  evolution  of  nitrogen. 

A  more  satisfactory  plan  seems  to  be  that  outlined  by 
K.  Baumann  and  A.  Bomer  :  The  remaining  portion,  100  c.c., 
from  the  zinc  sulfate  precipitate  is  mixed  with  excess  of  so- 
dium phosphomolybdate  (see  page  275),  by  which  the  meat- 
bases,  peptones,  and  ammonium  compounds  are  precipitated. 
This  precipitate  is  removed  by  filtration  under  pressure,  so  as 
to  draw  out  as  much  as  possible  of  the  mother-liquor,  and 
the  nitrogen  determined  as  usual.  The  nitrogen  due  to  pep- 
tone being  known,  that  due  to  meat-bases  and  ammonium 
compounds  can  be  calculated.  To  determine  the  ammonium 
compounds,  a  known  weight  of  the  original  sample  should  be 
distilled  with  barium  carbonate,  the  distillate  being  collected 
in  a  known  quantity  of  standard  acid,  which  is  afterward 
titrated. 

Meat-extracts  sometimes  contain  coagulable  proteids. 
These  may  be  estimated  by  rendering  the  filtered  solution 
distinctly  acid  with  acetic  acid  and  boiling  for  five  minutes. 
The  coagulum  may  be  weighed  directly  or  the  nitrogen  in  it 
estimated  by  the  Kjeldahl-Gunning  method  and  multiplied  by 
6.25  for  albumin. 


FLESH -FOODS  369 

As  solutions  of  proteids,  proteoses,  and  peptones  are  strongly 
levorotatory,  while  most  of  the  meat-bases  that  occur  in  these 
extracts  are  inactive,  some  information  might  be  gained  by 
examining  the  liquid  from  the  zinc  sulfate  precipitate  in  the 
polarimeter.  A  solution  that  had  no  appreciable  optic  activity 
would  not  be  likely  to  contain  much  peptone.  Another 
special  test  that  may  be  applied  to  this  liquid  is  the  so-called 
biuret  reaction.  A.  Bomer  applies  this  as  follows  :  The  filtrate 
from  the  zinc  sulfate  precipitation  is  decolorized  by  shaking 
with  animal  charcoal  and  the  zinc  sulfate  decomposed  by  excess, 
of  sodium  carbonate  or  cautious  addition  of  barium  hydroxid. 
The  filtered  solution  is  rendered  alkaline  with  sodium  hydroxid 
and  a  drop  or  two  of  very  dilute  solution  of  copper  sulfate 
added.  Peptones  give  a  rose-red  tint. 

Preservatives  may  be  added  to  meat-extracts,  although  this 
is  not  usual.  Boric  acid  will  be  most  likely  to  be  used,  and 
the  methods  on  page  89  will  suffice  for  its  detection.  Pois- 
onous metals  are  not  likely  to  be  present,  but  may  be  sought 
for,  if  deemed  necessary,  by  the  methods  given  on  pages  68 
to  72. 


APPENDIX 


ADDENDA 

To  page  237  : 

So-called  "  process"  or  "renovated"  butter,  made  by 
rendering  old  or  inferior  samples,  purifying  the  fat,  coloring, 
salting,  and  molding  it,  is  now  a  familiar  commercial  article. 
Process  butter  when  heated  in  a  dish  sputters  with  but  little 
foaming,  as  does  oleomargarin ;  but  yields  with  alcoholic 
soda  the  pineapple  odor,  as  does  butter.  The  fat  of  process 
butter  gives  refractometric  data  and  Reichert-Meissl  number 
similar  to  those  of  ordinary  dairy  butter,  but  is  said  to  give  a 
different  figure  with  Valenta's  test.  Precise  information  on 
the  last  point  is  not  at  hand.  If,  therefore,  a  sample  sputters  in 
the  pan,  but  gives  the  other  reactions  for  butter,  as  just  noted, 
it  may  be  assumed  to  be  process  butter.  W.  H.  Hess  and 
R.  E.  Doolittle  have  ascertained  that  the  curd  of  process  but- 
ter has  characteristic  qualities,  and  have  devised  the  following 
method  for  detecting  it : 

50  grams  of  the  sample  are  melted  in  a  beaker  at  about 
50°.  Ordinary  butter  yields  a  clear  fat  almost  as  soon  as 
melted,  while  with  process  butter  the  fat  may  remain  turbid 
for  a  long  while.  When  the  curd  has  largely  settled,  as-  much 
of  the  fat  is  poured  off  as  possible,  and  the  remaining  mix- 
ture is  thrown  on  a  wet  filter,  by  which  the  water  will  drain 
away,  carrying  the  soluble  proteids  and  salt.  A  few  drops 
of  acetic  acid  are  added  to  the  filtrate  and  the  mixture  is 
boiled.  The  filtrate  from  ordinary  butter  gives  but  a  slight 
milkiness,  but  that  from  process  gives  a  flocculent  precipitate. 

Quantitative  examination  is   made  by  dissolving  50  grams 


ADDENDA 

of  the  sample  in  ether  ;  if  it  is  ordinary  butter,  the  curd  is  so 
finely  divided  that  it  remains  suspended  for  some  time.  As 
much  as  possible  of  the  solution  is  decanted  and  the  mass 
transferred  to  a  separator,  the  casein,  water,  and  salt  removed, 
and  the  remainder  washed  three  times,  at  least,  with  ether  to 
remove  the  fat.  The  curd  is  collected  on  a  filter,  washed 
with  water,  and  the  nitrogen  determined  by  treating  the  pre- 
cipitate with  the  filter  by  the  Kjeldahl-Gunning  method.  The 
filtrate  from  the  curd  is  made  slightly  acid  with  acetic  acid, 
boiled,  the  precipitated  proteids  collected  on  a  filter,  and  the 
total  nitrogen  determined.  The  factor  6.25  may  be  used  in 
each  case  for  converting  the  nitrogen  into  proteids. 

A  distinction  between  ordinary  and  process  butter  may 
often  be  made  by  microscopic  examination  under  polarized 
light  with  crossed  nicols  (i.  e.t  dark  field),  when  the  process 
butter  appears  mottled,  owing  to  the  presence  of  crystals. 

To  page  239  : 

J.  F.  Geisler  found  paraffin  in  oleomargarin  ;  his  observa- 
tion has  been  confirmed  by  several  other  chemists.  Geisler 
uses  the  specific  gravity  of  the  rendered  fat  as  a  sorting  test, 
making  special  examination  only  of  samples  that  show  below 
0.9018  at  ~r^o-.  Microscopic  examination  under  polarized 
light,  with  and  without  selenite,  will  often  sh'ow  amorphous 
masses  of  paraffin  mixed  with  the  crystals  of  fat.  To  isolate 
the  paraffin,  Geisler  saponifies  2.5  grams  of  the  fat  with  20 
c.c.  of  alcohol  and  I  gram  of  potassium  hydroxid,  and  dilutes 
the  liquid  with  an  equal  bulk  of  water.  By  alternately  heat- 
ing and  cooling  the  liquid  much  of  the  unsaponifiable  matter 
may  be  collected.  It  is  also  possible  to  isolate  it  by  the  pro- 
cess given  on  page  165,  or  by  destroying  the  fat  by  strong 
sulfuric  acid.  It  must  be  borne  in  mind  that  most  fats  contain 
notable  amounts  of  unsaponifiable  matter,  and  hence  the 
material  must  be  identified  as  paraffin. 


372  FOOD    ANALYSIS 

SPECIFIC  GRAVITY  OF   WATER  FROM  o°  TO  100° 
Water  at  o°  =  0.99987  Water  at  4°  =  i.ooooo 


I   0.99992 

26     0.99686 

51    0.98772 

76    0.97438 

2          96 

27          60 

52       25 

77    0.97377 

3       99 

28       33 

53   0.98677 

78       16 

4    i  .00000 

29       05 

54       29 

79    0-97255 

5    0-99999 

30   0.99576 

55   0.98581 

80    0.97194 

6       97 

3i       77 

56       34 

81       32 

7       93 

32       47 

57   0.98486 

82    0.97070 

8       88 

33   0-99485 

58       37 

83       07 

9       82 

34       52 

59   0.98388 

84    0.96943 

10       74 

35       18 

60       38 

85    0.96879 

ii       65 

36   0.99383 

6  1   0.98286 

86       15 

12       54 

37       47 

62       34 

87    0.96751 

J3       43 

38       10 

63   0.98182 

88    0.96687 

14       29 

39   0.99273 

64       28 

89       22 

•  15       16 

40       35 

65    0.98074 

90    0.96556 

16       oo 

41   0.99197 

66       19 

91    0.96490 

17   0.99884 

42       58 

67   0.97964 

92       23 

18       65 

43       18 

68       08 

93    0.96356 

19       46 

44   0.99078 

69   0.97851 

94    0.96288 

20       25 

45       37 

70   0.97794 

95       19 

21          04 

46   0.98996 

7i       36 

96    0.96149 

22     0.99782 

47       54 

72   0.97677 

97    0.96079 

23          60 

48       10 

73       '8 

98       08 

24          36 

49    0.98865 

74   0.97558 

99    0.95937 

25          12 

50       19 

75   0.97498 

100    0.95866 

THERMOMETRIC    TABLE  373 

CORRESPONDENCE  OF  CENTIGRADE  AND  FAHRENHEIT  DEGREES 


0 

i 

2 

3 

4 

5 

6 

7 

8 

9 

20 

392.0 

393-8 

395-6 

397-4 

399-2 

401.0 

402.8 

404.6 

406.4 

408.2 

19 

374-0 

375-8 

377-6 

379-4 

381.2 

383-0 

384.8 

386.6 

388.4 

390.2 

18 

356.0 

357-8 

359-6 

361.4 

363-2 

365-0 

366.8 

368.6 

370.4 

372.2 

17 

338.0 

339-8 

341.6 

3434 

345-2 

347-o 

348.8 

350.6 

352-4 

354-2 

16 

320.0 

321.8 

323-6 

325-4 

327.2 

329-0 

330-8 

332.6 

334-4 

336-2 

15 

302.0 

303-8 

305.6 

3°7-4 

309.2 

311.0 

312.8 

3H.6 

3l6-4 

318.2 

14 

284.0 

285.8 

287.6 

289.4 

291.2 

293-0 

294.8 

296.6 

298.4 

303.2 

13 

266.0 

267.8 

269.6 

271.4 

273.2 

275.0 

276.8 

278.6 

280.4 

282.2 

12 

248.0 

249-8 

257.6 

253-4 

255-2 

257.0 

258.8 

260.6 

262.4 

264.2 

II 

230.0 

231.8 

233-6 

235-4 

237-2 

239.0 

240.8 

242.6 

244.4 

246.2 

10 

212.0 

213.8 

215.6 

217.4 

219.2 

221.0 

222.8 

224.6 

226.4 

228.2 

9 

194.0 

195.8 

197.6 

199.4 

201.2 

203.0 

204.8 

206.6 

208.4 

2IO.2 

8 

176.0 

177.8 

179.6 

181.4 

183.2 

185.0 

186.8 

188.6 

190.4 

192.2 

7 

158.0 

159.8 

161.6 

163.4 

165.2 

167.0 

168.8 

170.6 

172.4 

174.2 

6 

140.0 

141.8 

143  6 

145-4 

147-2 

149.0 

150.8 

152.6 

'54-4 

156.2 

5 

122.0 

123.8 

125.6 

127.4 

129.2 

I3I.O 

132.8 

134.6 

136.4 

138.2 

4 

104.0 

105.8 

107.6 

109.4 

III.  2 

II3.0 

II4.8 

116.6 

118.4 

120.2 

3 

86.0 

87.8 

89.6 

91.4 

93-2 

95-o 

96.8 

98.6 

100.4 

IO2.2 

2 

68.0 

69.8 

716 

73-4 

75-2 

77-o 

78.8 

80.6 

82.4 

84.2 

I 

50.0 

51.8 

53-6 

55-4 

57-2 

59-o 

60.8 

62.6 

64-4 

66.2 

0 

32.0 

33-8 

35-6 

37-4 

39-2 

41.0 

42.8 

44-6 

46.4 

48.2 

15.55°  c-  =  60°  F. 


o 

-I 

-2 

-3 

-4 

-5 

-6 

-7 

-8 

-9 

o 

32.0 

30.2 

28.4 

26.6 

24.8 

23.0 

21.2 

19.4 

17.6 

15.8 

-I 

14.0 

12.2 

10.4 

8.6 

6.8 

5-o 

3-2 

1.4 

-0.4 

-2.2 

-2 

-4.0 

-5-8 

-7.6 

-9-4 

-II.  2 

-13.0 

-I4.8 

-16.6 

-18.4 

-20.2 

-3 

-22.0 

-23-8 

-25.6 

-27.4 

-29.2 

-31.0 

-32.8 

-34-6 

-36.4 

-38.2 

-40°  C.  ==  -40°  F. 


374 


FOOD    ANALYSIS 


ELEMENTS,  SYMBOLS,  AND  ATOMIC  WEIGHTS 

Corrected  according  to  list  published  in  the  Journal  of  the  American  Chemical  Society, 

February,  1901. 


Aluminum,   .... 
Antimony,     
Argon 

Al 
Sb 
A 

27.1 
120.4 

•7Q    Q 

Necdymium,  .  .  . 
Neon,  
Nickel 

Nd 
Ne 
Ni 

143.6 
20 

eS  7 

Arsenicum,   .    . 
Barium,     

As 
Ba 

75-0 

1-27   A 

Nitrogen,  .... 
Osmium,  .... 

N 
Os 

14.04 
IQI 

Bismuth,  .  ... 
Boron,  

Bi 
B 

208.1 
ii 

Oxygen,  .... 
Palladium,  .... 

O 
Pd 

16 
IO7 

Bromin,  
Cadmium,  .... 
Calcium,  .... 

Br 
Cd 

Ca 

79-9 
112.4 
40.1 

Phosphorus,     . 
Platinum,     .... 
Potassium,   .... 

P 
Pt 
K 

31 

194.9 

39-  T  * 

Carbon,  .... 

c 

12 

Praseodymium,  .  . 

Pr 

140  c; 

Cerium,  .... 
Cesium,  .... 

Ce 

Cs 

139 
I  12  Q 

Rhodium,  .... 
Rubidium,  .  . 

Rh 
Rb 

103 

85  4 

Chlorin 

Cl 

Ruthenium, 

Ru 

101  7 

Chromium,  .... 
Cobalt,  
Columbium,  .  .  . 
Copper, 

Cr 
Co 
Cb 
Cu 

59 
93-7 
6s.  6 

Samarium,  .... 
Scandium,  .... 
Selenium,  .... 
Silicon,  .... 

Sm 

Sc 
Se 
Si 

150-3 

44.1 
79-2 
28.4 

Erbium,  .... 
Fluorin,  
Gadolinium,  .  .  . 
Gallium,  
Germanium,  .  .  . 
Glucinum,  .... 
Gold,  
Helium,  .... 

E 
F 

Gd 
Ga 
Ge 
Be 
Au 
He 

1  66 
19.05 

157 
70 

72.5 
197.2 

4  O 

Silver,  
Sodium,  
Strontium,  .... 
Sulfur,  
Tantalum,  .... 
Tellurium,  .... 
Terbium,  .... 
Thallium 

Ag 

Na 
Sr 
S 
Ta 
Te 
Tb 
Tl 

107.92 

23-05 
87.6 
32.07 
182.8 

127-5 
1  60 
204  15 

Hydrogen,  .... 
Indium,  .  .  .  .  . 

H 
In 

1.008 

114 

Thorium,  .... 
Thulium 

Th 
Tm 

232.6 
1  70.7 

lodin 

I 

126  85 

Tin 

Sn 

I  IQ 

Iridium,  ....'. 
Iron, 

Jr 
Fe 

I93-I 
ce  Q 

Titanium,  .... 
Tungsten 

Ti 
W 

.48.15 
l84 

Krypton,  .  . 

Kr 

8l.8 

Uranium 

u 

2^0  6 

Lanthanum,  .  .  . 
Lead 

La 
Pb 

138.6 
206  92 

Vanadium,  .... 

V 

x 

51-4 
128 

Lithium,  

Li 

7.0^ 

Ytterbium,  .... 

Yb 

173.2 

Magnesium,  .... 

Mg 

24.3 

Yttrium,  .... 

Y 

89 

Manganese 

Mn 

cc 

Zinc 

Zn 

65  4 

Mercury 

2OO 

Zirconium 

Zr 

QO  A 

Molybdenum,  .  ,  . 

Mo 

96 
^^x^-^r 

REFERENCES 


1  Laurent.     Das  optische  Drehungsvermogen. 

2  Bull.  46,  Rev.  Ed.,  U.  S.  Dept.  of  Agriculture. 

3  Bull.  176,  U.  S.  Geological  Survey. 

4  Dingler's  Polyt.  Jour.,  232  (1879),  461. 

258. 
551- 

12. 

Com'l  Org.  Anal.,  I,  66. 
9       «•         »         •«       111,1,497-8-9- 
10  Bull.  59,  U.  S.  Dept.  of  Agriculture. 


•  umgier  s  roiyi.  jo 

5  J.  A.  C.  S.,  1899, 

6  J.  C.  S.,  1883,  551 

7  J.  A.  C.  S.,  1901, 


"     13,5," 

13  <<          «  «  «  <« 

14  ((          «  «  <«*  (( 

15  J.  A.  C.  S.,  1901,  60-1. 

16  jCom'l  Org.  Anal.,  I,  371-2. 

17  Bull.  123  (1896),  Connecticut  Agric.  Exp.  Station. 

18  Analyst,  1897,  287.      (The  reference  is  misplaced  ;  see  list  of  corrections.) 

19  Com'l  Org.  Anal.,  II,  1,  85. 

20  Chem.  Anal.  Oils,  Fats,  and  Waxes,  165. 

21  J.  A.  C.  S.,  1900,453;   1901,  I. 

22  J.  A.  C.  S.,  1897,  796. 

23  Analyst,  1890,  170. 

24  T.  A.  C.  S.,  1896,428. 

25  J.  A.  C.  S.,  1900,  207. 

26  J.  A.  C.  S.,  1898,  no. 

27  J.  A.  C.  S.,  1898,  207. 

Bull.  13,  7,  U.  S.  Dept.  of  Agriculture. 

29  Food  Adulteration  and  its  Detection. 

30  Bull.  13,  7,  U.  S.  Dept.  of  Agriculture. 

31  Com'l  Org.  Anal.,  Ill,  2,  547. 

32  Analyst,  1899,  281. 

33  See  Zeit.  Anal.  Chem.,  Jan.,  1901,  fora  new  process  for  separating  theo 

bromin  and  caffein  from  cacao. 

34  Bull.  13,  7,  U.  S.  Dept.  of  Agriculture. 

35  Mikroskopie  der  Nahrungs  und  Genussmittel. 

36  «  <(  «  i<  " 

37  Com'l  Org.  Anal.,  I,  545. 

38  «  «<  «         IV 

39  Flesh -Foods. 


375 


1.  Tea  ( Thea  chinensis  Link.). 

2.  Mate-    (Ilex  paraguayensis    Lam- 
bert). 

3.  Thea  japonica  Baillon. 

4.  Hawthorn  (Cratcegtts  sp.). 

5.  Box     elder     (Negundo     aceroides 
Moench.). 

6.  Horse  chestnut  (sEsculus  hippocas- 
tanum  L.). 

7.  Sycamore    (Plafanus    occidentalis 
L.). 

8.  Rose  (Rosa  sp.). 

9.  Plum  (Prunus  sp.). 

10.   Elm  (U/mus  fulva  Michx.). 


11.  Ash  (Fraxinus  sp. ). 

12.  Willow  (Sa/ixsp.). 

13.  Willow  (Satixsp.). 

14.  Beech  (Fagus  ferruginea  Ait.). 

15.  Oak  ( Quercus  sp. ) . 

1 6.  Missouri    currant    (Ribes  aureum 
Pursh.). 

17.  Ash  ( Fraxinus  sp. ) . 

18.  Red  currant  (Ribes  rubrum  L.). 

19.  Birch  (Betula  lenta  L.). 

20.  Poplar  (Populus  alba  L.). 

21.  Raspberry  (Rubus  sp.). 

22.  New  Jersey  Tea  ( Ceanothus  Ameri- 

canus  L. ). 


Potato. 


Arrowroot. 


Wheat. 


%*m 


Bean. 


Pea. 


Barley. 


i  I 


Rye. 


Rice. 


Maize. 


Ginger. 


Sago. 


Buckwheat. 


o 


VI 


Oat. 


NDEX 


AHRASTOL,  84 
Acetyl  number,  162 

value,  162 

Acidity,  total,  349 
Acid  mercuric  iodid,  230 

nitrate,  213 

value,  150 

Acorn  starch,  95 
Acrinyl  isothiocyanate,  318 
Adams'  method,  203 
African  pepper,  303 
Albumin,  193,  210,  212 
Albuminoid  nitrogen,  46 
Alcohol,  detection,  342 

—  determination,  343 
—  ethyl,  64 

methyl,  65 

— detection,  356 

tables,  344-5-6 

Alcoholic  beverages,  326 

Ale,  332,  333 

Allen,  A.  H.,9,i;,  28,31,  68,69,78, 
109,  118,  140,  141,  182,  260,  261, 
286,  287,  289,  305,  306,  319,  326, 
333.  355.  360,  363,  366 

Allihn's  method,  119,  121 

Allspice.  311 

Allyl  isothiocyanate,  317 

Almen's  reagent,  21 1 

Alum  in  bread,  107 

—  in  flour,  IOI 
Alumina-cream,  123 
Ammonium  in  baking  powders,  113 
Amphoteric  milk,  194 

Angell,  A.,  145 

Annatto,  detection,  217,  220 

Apple  brandy,  329 

whiskey,  329 

Arata's  test,  77 
Arachidic  acid,  178 
ArachiHin,  177 
Arachis  oil,  177 
Archbutt,  L.,  151,  178,  180 


Archil  in  wine,  352 
Arrow- root  starch,  94 
Arsenic,  detection,  71 
Asaprol,  84 
Aschmann   F.  J. ,  225 
Ash,  47 

Ashby,  A.,  288 
Astruc,  H.,  340 
Axtell,  F.  C.,  58 


BABCOCK'S  method,  202,  204 
Baking  powders,  no 

soda,  109 

Ballantyne,  H.,  152 
Banana  starch,  94 
Barium  in  pepper,  305 
Barley,  101,  103 

starch,  95 

Bases,  meat-,  366 
Battershall,  J.  B.,  254,  256 
Baudouin's  test,  170 
Baumann,  A.,  368 
Beam,  W.,  146,  205 
Bean  flour,  103 

—  starch,  95 
Bechi's  test,  169 
Beckmann,  E.  O.,  135-137 
Beef  fat,  191 

—  stearin,  189 
Beer,  332 

-  root,  334 
Bell,}.,  277 
Benzene,  65 
Benzoates,  88 
Benzoic  acid,  84,  88 
Berthelot,M.,  21,  148 
Beurre  rouge,  239 
Bevan,  E.  J.,  223 
Bigelow,  W.  D.,  89,  103,  230 
Bird  pepper,  303 
Birotation,  215 
Bitters  in  beer,  355 


377 


373 


INDEX 


Bitteryst,  A.,  280 

Biuret  reaction,  369 

Bjorkland's  test,  183 

Blue  miik,  224 

Blyth,  A.  W.,  107,  243,  261,  304 

Bodmer,  R.,  70 

Boiled  milk,  detection,  223 

Boiling-point,  21 

Bonier,  A.,  366,  368 

Borax,  85,  89 

Boric  acid,  85,  89 

Borntrager,  A  ,  312 

Borofluorids,  86,  90 

Boseley,  L.  K.,  21 1,  223,  325 

Bouquet,  335 

Brandy,  330 

apple,  330 

Bread,  105 

—  commercial,  106 
Bremer,  H.,  362 
Bromas,  282 

Bromin,  thermal  value,  152 
Brown,  J.  C,  297,  300,  302 
Buckwheat,  101,  104 

starch,  96 

Bumping,  prevention,  54,  59 
Burners,  62,  63 
Batter,  231 

cacao-,  182 

—  colors,  237 

composition,  232 

fat,  191 

milk,  196 

peanut,  177 

vegetable,  182 

Butyrorefractometer,  157 


CACAO,  274 

—  butter,  182 

essence,  278 

husks,  278 

masse,  278 

red,  276 

starch,  95 

Caffearin,  262 

Caffein,  252,  263,  27 f,  275 

determination,  257,  268 

Caffetannic  acid,  262 

Caldwell,  G.  C,  37 

Candies,  138 

Cane-sugar,  113,  126,  219 

Canna  starch,  94 

Caper  tea,  256 

Caramel,  127,  129,  272,  352 


Carr,0.,39 
Caryophyllin,  315 
Casein,  192,  210,  212 
Cassal,  C.  A.,  270 
Cassia,  312 

— . ore,  314 

Catsup,  323 

Centrifuge,  6 1 

Cereals,  99 

Champagne,  3^6 

Chandler,  C.  F.,  27 

Chattaway,  W.  A.,  151,  244,  247 

Cheese,  339 

Chicory,  266 

Chillies,  303 

Ching  suey,  256 

Chittendcn,  R.  H.,  loo 

Chocolate,  274 

nuts,  277 

Cholesterol,  160 
Chr.imium,  detection,  69 
Cider,  326 

vinegar,  284 

Cinnamon,  312 
-  oil,  314 

starch,  95 

Clove  oil,  315 

Cloves,  315 

Cobalt  nitrate  test,  113 

Cochineal,  67 

Cochran,  C.  B  ,  190,  196,  197,  198 

Cocoa,  274 

Cocoas,  soluble,  278 

Coconut  oil,  182 

olein,  182 

stearin,  182 


Coffee,  262 


essence,  273 
extracts,  273 


Colors,  72-82 

in  butter,  237 

in  candies,  139 

in  meat,  363 

in  milk,  217,  218 

in  wine,  351 

—  test  for  oil-,  141 
Colostrum,  198 
Colza  oil,  181 
Condensed  milk,  225 
Condenser,  42,   57 
Condiments,  283 
Confections,  138 
Congou  paste,  256 

tea,  254 

Constants  for  oils,  168 


INDEX 


379 


Copper,  detection,  69 

—  hydroxid  mixture,  46 

—  in  bread,  108 

in  flour,  102 

Coriander  seed,  301 
Corn,  Dhoura,  300 

oil,  170 

Cottonseed  oil,  175 

stearin,  175 

Counley,  A.  T.,  70,  257 

Cox,  G.  S.,  204,  326 

Crampton,  C.   A.,   Ill,  130,  239,352 

Cream,  196 

evaporated,  225 

of  tartar,  109 

Crude  fiber,  46 
Cumarin,  321 


DAVY,  E.  W.,  342 
De  Koningh,  L. ,  144 
Delican's  titer-test,  20 
Desserts,  324 
Dextrin  in  honey,  135 

—  in  wine,  349 
Dextrosazone,  114 
Dextrose,  determination,  116 
Dhoura  corn,  300 

starch ,  300 

Distillation,  54 
Doolittle,  R.  E. ,  370 
Drying  of  oils,  158 

ovens,  37 

property,  158 

Dry  wine,  336 
Dupouy,  R.,  223 
Dyer,  B.,  270,  313 


ELEADIN  test,  156 
Electrolytic  apparatus,  122 

methods,  65 

Elements,  374 
Ergot,  102 
Erucin,  181 
Essence  of  cacao,  278 

of  coffee,  273 

Ether  purification,  50 

Eugenic  acid,  315 

Eugenol,  315 

Evaporated  cream,  225 

Ewell,  E.  E.,  215,  217,  281,  282 

Extract,  36 

Extraction  apparatus,  49,  52 


Extracts,  coftee,  273 

malt,  359 

meat,  366 


FACING  coffee,  265 
tea,  255,  258 


Farnsteiner,  K.,  283 

Fat  of  milk,  192. 

Fats,  140 

Fehling's  solution,  116 

Fermented  milk,  248 

Fiber,  crude,  46 

Filter-tubes,  117,  120 

Flesh-foods,  360 

Flour,  98,  101 

Fluorescence,  31 

Fluorids,  86,  90 

Foreign  leaves  in  tea,  260 

Formaldehyde,  84,  90,  220 

Formalin,  84,  220 

Fractional  distillation,  60 

Fuchsin  in  wine,  352 

Furfural  test,  170 

Fusel  oil,  determination,  353 


GALACTOSAZONE,  115 
Gallisin,  130,  354 
Geisler,  J.  F.,  226,  237,  371 
Gelatin,  detection,  219,  324 
German  beer,  332 
Gerrard,  A.  W.,  118 
Gin,  331 
Ginger,  305 

starch,  94 

Gingli  oil,  180 
Gliadin,  98 
Globulin,  193 
Glucose,  130 

vinegar,  284 

Glutenin.  98, 
Glycerol  in  wine,  350 

soda,  146 

Glycogen,  362 
Gomberg,  H.,  257 
Graham  flour,  101 
Grape-juice  vinegar,  284 
Grape-sugar,  130 
Gum  in  wine,  349 
Gutzert's  test,  72 
Gypsum  in  bread,  108 

HAGER,  H.,  9,  183,  260,  342 
Halphen's  test,  169 


INDEX 


Hardy,  J.,  342 

Hehner,  O.,   145,  152,  185,  207,  221, 
231,  270,  286,  289 

value,  158 

Heisch,  C.,  294,  296 

Henzold,  O.,  294 

Hess,  W.  H.,  54,  320,  370 

Hollands,  331 

Honey,  132 

Hopkins,  C.  G.,  176,  177 

Horseflesh,  detection,  362 

Hubl's  reagent,  142 

Hydrometers,  15 

ICE-CREAM,'324 

Immiscible  solvents,  53 
Improvers,  meat,  364 
Index  of  refraction,  157 
Infected  milks,  224 
Insoluble  acids,  158 
Inversion  methods,  124,  228 
Invert-sugar,  113,  119,  230 
lodin  number,  142 

value,  142 

Irish  whiskey,  330 

JAMS,  324 

Jean,  F. ,  236 

Jellies,  324 

Jones,  B.  W.,  189,  235 

KAYSER,  R.,  326 

Kefyr,  249 

Kjeldahl-Gunning  method,  41 

Knorr,  A.  E.,  52,  ill,  117 

Konig,  J.,  138,    249,   263,   272,    307, 

313 

Kottstorfer  number,  148 
Kraemer,  H  ,  103,  105 
Kreatin,  366 
Kreatinin,  366 
Krug,  W.  H.,  96 
Kumiss,  248 
Kunze,  W.  E.,  274,  275 

LACTOSAZONE,  115 
Lactose,  131,  193,  213 
Ladd,  E.  F.,  257 
Lager  beer,  332 
Lard,  184 

Laurent  polarimeter,  29 
Laureol,  182 
Laurin,  182 


Leach,  A.  E.,  218,  227 
Lead,  detection,  69 

number,  297 

subacetate,  123 

Leavening  materials,  109 
Leffmann-Beam  method,  205 
Leguminous  flours,  103 
Lemon  juice,  322 

sirup,  322 

Lentil  starch,  95 
Leonard,  N.,  91 
Levulosazone,  214 
Lewkowitsch,  J.,  141,  189 
Lieben's  test,  342 
Lie  tea,  255 
Lignoceric  acid,  178 
Litmus,  66 
Livache's  test,  158 
Long  pepper,  301 
Low,  A.  H.,  238 
Low-pressure  distillation,  58 
Low  wine,  284,  328 
Lubricants,  59 
Lythgoe,  H.  €.,219 


MACE,  308 

—  false,  310 
Maize,  loi,  103,  105 

oil,  176 

starch,  96 

Malt  extract,  97,  359 

liquors,  331 

Maltosazone,  115 
Malt  vinegar,  284 
Maple  sugar,  132 

syrup,  132 

Maranta  starch,  94 
Marmalade,  325 
Matthews,  J.  M.,  78 
Maumene's  test,  151 
McElvoy,  K.  P.,  112,230 
McGill,  A.,  13,  269 
Mead,  334 
Meade,  R.  K. ,  65 
Meal,  98 
Meat  bases,  366 

extracts,  366 

Meats,  canned,  365 

infected,  365 

Meissl,  E.,  146 
Melting-point,  16 
Mercuric  iodid,  acid,  230 

—  nitrate  acid,  213 
Metals,  poisonous,  68 


INDEX 


Methyl  alcohol,  65 

detection,  356 


orange,  (,6 

Microscope,  32 
Milk,  192   ' 

-  boiled,  195 
Miscible  solvents,  49 
Mitchell,  C.  A.,  152,  185,  231,  366 
Mixed  flours,  103 
Moeller,  J.,  255,  298 
Mohr's  cubic  centimeters,  29 
Molasses,  128 
Moor,  C.  G.,  70,  151,  225,   244,  247, 

273,  286,  287,  306 
Mother  cloves,  315 

starch,  94 

Mulliken,  S.  P.,  356 
Must,  335 
Mustaid,  317 

-oil,  317 
Muter,  T.,  93,   144 
Myristic  acid,  307 
Myronic  acid,  317 
Myrosin,  317 


NAPHTHOL,  84,  91 
Nickel  detection,  69 
Nitric  acid  test,  141 
Nitrogen,  albuminoid,  46 

—  total,  41 
Normal  weight,  29 
Nucoline,  182 
Nutmeg,  307 

oil,  307 

Nutshells,  299 


OATS,  101,  103 
Oat  starch,  96 
Ogden,  A.  W.,  132 
Oil,  arachis,  177 
cassia,  314 

cinnamon,  314 

—  cloves,  315 

—  coconut,  182 

—  colza,  181 

—  corn,  176 

cottonseed,  175 

gingli,  180 

—  maize,  176 

mustard,  317 

—  nutmeg,  307 

—  olive,  171 
pepper,  292 


Oil,  rape,  181 

—  sesame,  180 

teel, 

Oleomargarin,  234 
Oleorefractometer,  157 
Olive  oil,  172 

stones,  297 


Original  solids,  286 
Osborne,  T.  B.,  39,  98,  100 
Ovens,  37,  39 


PARAFFIN  in  oleomargarin,  370 

Parsons,  C.  C.,  41 

Paul,  B.  H.,  70,  257,  268,  269 

Pea  flour,  103 

Peanut  butter,  177 

Pearmain,  T.  M.,  151,  225,  236,  244, 

247 

Pea  starch,  95 
Pekoe  tea,  254 
Pepper,  290 

—  African,  303 
bird,  303 

cayenne,  303 

Pepperette,  297 
Pepper,  long,  301 

starch,  96 

Peptones,  determination,  366 
Perry,  326 
Petroleum  spirit,  65 
Phenol,  91 
Phenol  phthalein,  66 
Phenylhydrazin  test,  114 
Phillips,  F.  C,  59 
Phytosterol,  1 60 
Piperidin,  291 
Piperin,  291 
Plastering  of  wine,  339 
Platinum,  care  of,  63 
Poisonous  metals,  68 
Poivrette,  297 
Polarimetry,  22,  123,  357 
Porter,  332 
Potato  flour,  104 

—  starch,  94 
Prescott,  A.  B.,  55 
Preservaline,  85 
Preservatives,  83,  86,  223 
Priest,  M.,  273 
Process  butter,  370 

Proteids,  determination,  209,  366 
Proteoses,  determination,  366 
Prune  juice,  detection,  352 
Prussian  blue,  detection,  258 


INDEX 


Putrefaction,  detection,  364 
Pyknometer,  10 


RAPE  oil,  181 

Recknagel's  phenomenon,  194 
Red  milk,  224 
Reduction,  1 21 
Refraction  index,  157 
Refractometer,  157 
Reichert,  E.,  145 
Reichert-Meissl  number,  146 
Reichert  number,  146 
Reinsch's  test,  71 
Renovated  butter,  370 
Rex  magnus,  85 
Rice,  101-4 

starch,  96 

Richardson,  C. ,    294,   296,  304,  307, 

308,  311,313,  316,  317 
Richmond,  H.  D.,  91,   194,  196,  201, 

204,  207,  211,  216,  223 
Ricketts,  P.  de  P.,  27 
Ritthausen  method,  209 
Rock  and  rye  drops,  139 
Romijn,  G.  J.,  222 
Root  beer,  334 
Ropy  milk,  225 
Rosier,  C.  H.,  223 
Rum,  331 

Rye  flour,  99,  101,  104 
starch,  95 


-SACCHARIN,  84,  88 

Sago  starch,  95 

Salicylic  acid,  83,  87 

Salol,  91 

Sand,  65 

Saponification  equivalent,  150 

value,  148 

Sawdust  in  flour,  105 
Scales  for  polarimeter,  29 
Scheibler's  method,  30 
Schmidt  and  Hansch  scale,  29 
Schnapps,  331 
Schumann,  O.,  21 
Scotch  whiskey,  330 
Scudder,  H.,  356 
Separated  milk,  196 
Sesame  oil,  180 
Silicofluorids,  86,  90 
Simons,  F.  D. ,  130,  352 
Sinalbin,  317 
Sinapin  thiocyanate,  317 


Sirup,  128 

Smith,  A.  W.,  284,  288,  341 
Smith,  H.  M.,  91 
Sodium  benzoate,  83,  88 

—  phosphomolybdate,  275 
Solidifying-points,  16 
Solids,  original,  286 
Soluble  acids,  158 

cocoas,  278 

Solvents,  immiscible,  53 

misciUe,  49 

Souchong  tea,  254 
Soxhlet,  F  ,  49,  116,  119 
Spain,  E.,  309,  363 
Specific  gravity,  9,  140 

—  bottle,  10 

rotatory  power,  28 

temperature  reacton,  152 

Spectroscope,  30 

Spirit,  essig,  287 

Spirits,  327 

Sprengel  tube,  II 

Standard  solutions,  65 

Stannous  chlorid  in  bread,  108 

Starch,  92 

Starches,  characters  of,  94-6 

Stearin,  beef,  189 

coconut,  182 

cottonseed,  176 

Stock,  W.  F.  K.,  190,  294,  306 

Stokes,  A.  W.,  219,  228,  294,  303 

Stout,  332 

Stutzer's  method,  46,  245 

Sucrose,  113,  219 

Sublimation,  54,  60 

Sugar,  cane-,  113,219 

Sugars,  116 

Sulfates  in  baking  powders,  113 

Sulfites,  85,  350 

Sulfur  chlorid  test,  189 

Sulfuric  acid  in  vinegar,  289 

Sulfurous  acid  determination,  350 

Sweetser,  W.  S.,  103 

Symbols,  374 


TABLE  accessories,  323 
Taenia,  forms  of,  365 
Tallow,  .189 
Tapeworm,  365 
Tapioca  starch,  95 
Tartaric  acid,  277,  313 
Tea,  25 1 
Teeloil,'i8o 
Terra  alba  in  bread,  1 08 


INDEX 


383 


Thein,252 

Theobromin,  274,  275,  280 

Thermal  reactions,  151,  152 

Thompson,  R.  T.,  85,  152,  220 

Thome,  L.  T.,  58 

Tin  detection,  69,  70 

—  in  bread,  108 
Titer-test,  20 
Trichina,  365 
Turmeric,  310 

—  starch,  94 


ULTRAMARINE  blue,  126 
Unsaponifiable  matter,  165 


VALENTA'S  test,  150 

Vanilla  extract,  320 

Vanillin,  321 

Van  Slyke,  L.  L. ,  198,  240,  247 

Vegetable  butter,  182 

Vegetal  ine,  182 

Vieth,  P.,  196,  214,  216,  248 

Vinegar,  283 

—  cider,  284 

malt,  285 

spirit,  284 

wine,  283 

Viscosity,  164 
Volatile  acid,  145,  234 


Voorhees,  E.  B.,  98,  100 
Vulte,  H.  T.,  177 


WATER  determination,  36 

—  specific  gravity  of,  372 
Weigmann,  H.,  275 
Weissbier,  332 
Werner-Schmid  method,  204 
Weston  distillation  apparatus,  56 
Weslphal  balance,  13 

Wheat,  98,  99,   101,   103 

starch,  95 

Whey,  196 
Whiskey,  328 

apple,  329 

-  Irish,  330 

Scotch,  330 

Wild's  scale,  29 

Wiley,  H.  W.,  27,  34,  52,  70,  96,  113, 

117,  184,  213,  215 
Wine,  335 
low,  284,  328 

—  vinegar,  283 

Winton,   A.    L.,  284,  295,   302,  311, 

3l6>3i7 
Wool  test,  77,  127 


XA\THIN,  366 

ZINC,  detection,  69,  70 


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meet  previous  retail  discounts.  Upon  receipt  of  the  advertised  price  any 
book  will  be  forwarded  by  mail  or  express,  all  charges  prepaid. 


ANATOMY. 

MORRIS.  Text-Book  pt  Anatomy,  ad  Edition.  Revised  and 
Enlarged.  790  Illustrations,  214  of  which  are  printed  in  coldrs. 
Thumb  Index  in  Each  Copy.  Cloth,  $6.00 ;  Leather,  $7.00 

"  The  ever-growing  popularity  of  the  book  with  teachers  and  students 

is  an  index  of  its  value." — Medical  Record,  New  York. 

BROOMELL.  Anatomy  and  Histology  of  the  Human  Mouth 
and  Teeth.  284  Illustrations.  $4. 50 

CAMPBELL.  Dissection  Outlines.  Based  on  Morris'  Anatomy, 
ad  Edition.  .50 

DEAVER.     Surgical  Anatomy.     A  Treatise  on  Anatomy   in  its 
Application  to  Medicine  and  Surgery.    With  400  very  Handsome  full- 
page  Illustrations  Engraved  from  Original  Drawings  made  by  special 
Artists  from  dissections  prepared  for  the  purpose.     Three  Volumes. 
Cloth,  $21.00;  Half  Morocco  or  Sheep,  $24.00;  Half  Russia,  $27.00 

GORDINIER.  Anatomy  of  the  Central  Nervous  System. 
With  271  Illustrations,  many  of  which  are  original.  Cloth,  $6.00 

HEATH.    Practical  Anatomy.    8th  Edition.    300  Illus.          $4.25 

HOLDEN.     Anatomy.    A  Manual  of  Dissections.    Revised  by  A. 
HKWSON,  M.D.,  Demonstrator  of  Anatomy,  Jefferson  Medical  College, 
Philadelphia.     320  handsome   Illustrations.     7th    Edition.     In   two 
.compact  i2mo  Volumes.    850  Pages.    Large  New  Type.  Just  Ready. 
Vol.    I.    Scalp— Face— Orbit— Neck— Throat— Thorax— Upper  Ex- 
tremity. $'.50 
Vol.  II.    Abdomen — Perineum — Lower     Extremity — Brain — Eye — 
Ear — Mammary  Gland — Scrotum — Testes.               #1-50 

HOLDEN.  Human  Osteology.  Comprising  a  Description  of  the 
Bones,  with  Colored  Delineations  of  the  Attachments  of  the  Muscles. 
The  General  and  Microscopical  Structure  of  Bone  and  its  Develop- 
ment. With  Lithographic  Plates  and  numerous  Illus.  8th  Ed.  $5.25 

HOLDEN.     Landmarks.    Medical  and  Surgical.    4th  Ed.  .75 

HUGHES  AND  KEITH.  Dissections.  In  three  Parts  :  I,  Upper 
and  Lower  Extremity;  II,  Abdomen,  Pelvis;  III,  Perineum, 
Thorax.  With  Colored  and  other  Illustrations.  In  Press. 

MACALISTER.  Human  Anatomy.  Systematic  and  Topograph- 
ical. 816  Illustrations.  Cloth,  $5.00;  Leather,  $6.00 

McMURRICH.     Embryology.     Illustrated.  In  Press. 

MARSHALL.  Physiological  Diagrams.  Life  Size.  Colored. 
Eleven  Life-Size  Diagrams  (each  seven  feet  by  three  feet  seven 
inches).  Designed  for  Demonstration  before  the  Class. 

In  Sheets,  Unmounted,  $40.00;  Backed  with  Muslin  and  Mounted 
on  Rollers,  $60.00 ;  Ditto,  Spring  Rollers,  in  Handsome  Walnut  Wall 
Map  Case,  $100.00;  Single  Plates — Sheets,  $5.00 ;  Mounted,  $7.50. 
Explanatory  Key,  .50.  Purchaser  must  pay  freight  charges. 

POTTER.  Compend  of  Anatomy,  Including  Visceral  Anatomy. 
6th  Ed.  16  Lith.  Plates  and  117  other  Illus.  .80  ;  Interleaved,  $1.00 

WILSON.    Anatomy,     nth  Edition.    429  Illus.,  26  Plates.      $5.00 

WINDLE.    Surface  Anatomy.    Colored  and  other  Illus.        $1.00 


SUBJECT  CATALOGUE. 


BRAIN  AND  INSANITY  (see  also 
Nervous  Diseases). 

BLACKBURN.  A  Manual  of  Autopsies.  Designed  for  the  Use 
of  Hospitals  for  the  Insane  and  other  Public  Institutions.  Ten  full- 
page  Plates  and  other  Illustrations.  fi-^S 

DERCUM.     Mental  Therapeutics,  Rest,  etc.        Nearly  Ready. 

GORDINIER.  The  Gross  and  Minute  Anatomy  of  the  Central 
Nervous  System.  With  full-page  and  other  Illustrations.  $6.00 

HORSLEY.  The  Brain  and  Spinal  Cord.  The  Structure  and 
Functions  of.  Numerous  Illustrations.  $2.50 

IRELAND.    The  Mental  Affections  of  Children,    zd  Ed.    $4.00 

LEWIS  (BEVAN).  Mental  Diseases.  A  Text-Book  Having 
Special  Reference  to  the  Pathological  Aspects  of  Insanity.  26  Litho- 
graphic Plates  and  other  Illustrations.  2d  Ed.  $7-°° 

MANN.  Manual  of  Psychological  Medicine  and  Allied 
Nervous  Diseases,  $3.00 

PERSHING.  Diagnosis  of  Nervous  and  Mental  Disease. 
Illustrated.  Just  Ready.  $'-25 

REGIS.  Mental  Medicine.  Authorized  Translation  by  H.  M. 
BANNISTER,  M.D.  $2.00 

SHUTTLEWORTH.     Mentally  Deficient  Children.          $1.50 

STEARNS.  Mental  Diseases.  With  a  Digest  of  Laws  Relating 
to  Care  of  Insane.  Illustrated.  Cloth,  $2. 75  ;  Sheep,  $3. 25 

TUKE.  Dictionary  of  Psychological  Medicine.  Giving  the 
Definition,  Etymology,  and  Symptoms  of  the  Terms  used  in  Medical 
Psychology,  with  the  Symptoms,  Pathology,  and  Treatment  of  the 
Recognized  Forms  of  Mental  Disorders.  Two  volumes.  $10.00 

WOOD,  H.  C.    Brain  and  Overwork.  .40 


CHEMISTRY  AND  TECHNOLOGY. 

Special  Catalogue  of  Chemical  Books  sent  free  upon  application. 

ALLEN.    Commercial   Organic   Analysis.    A  Treatise  on  the 

Modes  of  Assaying  the  Various  Organic  Chemicals  and  Products 

Employed  in  the  Arts,  Manufactures,  Medicine,  etc.,  with  concise 

methods  for  the  Detection  of  Impurities,  Adulterations,  etc.     8vo. 

Vol.  I.  Alcohols,  Neutral  Alcoholic  Derivatives,  etc.,  Ethers,  Veg- 
etable Acids,  Starch,  Sugars,  etc.  sd  Edition.  $4-50 

Vol.  II,  Part  I.  Fixed  Oils  and  Fats,  Glycerol,  Explosives,  etc. 
3d  Edition.  $3-5° 

Vol.  II,  Part  II.  Hydrocarbons,  Mineral  Oils,  Lubricants,  Benzenes, 
Naphthalenes  and  Derivatives,  Creosote,  Phenols,  etc.  sd  Ed.  £3.50 

Vol.  II,  Part  III.  Terpenes,  Essential  Oils,  Resins,  Camphors,  etc. 
3d  Edition.  Preparing. 

Vol.  Ill,  Part  I.  Tannins,  Dyes  and  Coloring  Matters.  3d  Edition. 
Enlarged  and  Rewritten.  Illustrated.  $4-S° 

Vol.  Ill,  Part  II.  The  Amines,  Hydrazines  and  Derivatives, 
Pyridine  Bases.  The  Antipyretics,  etc.  Vegetable  Alkaloids,  Tea, 
Coffee,  Cocoa,  etc.  8vo.  2d  Edition.  $4-5° 

Vol.  Ill,  Part  III.  Vegetable  Alkaloids,  Non-Basic  Vegetable  Bitter 
Principles.  Animal  Bases,  Animal  Acids,  Cyanogen  Compounds, 
etc.  2d  Edition,  8vo.  $4. 50 

Vol.  IV.    The  Proteids  and  Albuminous  Principles,    ad  Ed.      £4.50 


MEDICAL   BOOKS. 


BAILEY  AND  CADY.     Chemical  Analysis.    Just  Ready.   #1.25 

HARTLEY.  Medical  and  Pharmaceutical  Chemistry.  A 
Text-Book  for  Medical,  Dental,  and  Pharmaceutical  Students.  With 
Illustrations,  Glossary,  and  Complete  Index,  sth  Edition.  $3.00 

HARTLEY.  Clinical  Chemistry.  The  Examination  of  Feces, 
Saliva,  Gastric  Juice,  Milk,  and  Urine.  $1.00 

BLOXAM.  Chemistry,  Inorganic  and  Organic.  With  Experi- 
ments, gth  Ed..  Revised.  281  Engravings.  Preparing. 

CALDWELL.  Elements  of  Qualitative  and  Quantitative 
Chemical  Analysis.  3d  Edition,  Revised.  $1.00 

CAMERON.    Oils  and  Varnishes.    With  Illustrations.          $2.25 

CAMERON.     Soap  and  Candles.     54  Illustrations  $2.00 

CLOWES  AND  COLEMAN.  Quantitative  Analysis,  sth 
Edition.  122  Illustrations.  $3-5° 

COBLENTZ.  Volumetric  Analysis.  Illustrated  Just  Ready.  £1.25 

CONGDON.  Laboratory  Instructions  in  Chemistry.  With 
Numerous  Tables  and  56  illustrations.  Just  Ready.  $1.00 

GARDNER.  The  Brewer,  Distiller,  and  Wine  Manufac- 
turer. Illustrated.  $1.50 

GRAY.  Physics.  Volume  I.  Dynamics  and  Properties  of  Matter. 
350  Illustrations.  Just  Ready.  $4-5° 

GROVES  AND  THORP.    Chemical  Technology.    The  Appli- 
cation of  Chemistry  to  the  Arts  and  Manufactures. 
Vol.  I.  Fuel  and  Its  Applications.     607  Illustrations  and  4  Plates. 

Cloth,  $5.00;  ^Mor.,$6.so 


Vol.11.    Lighting.      Illustrated.  Cloth,  $4.00 ;  J<j  Mor.,  $5.50 

Vol.  III.  Gas  Lighting.  Cloth,$3.5o;  %Mor.,$4.so 

Vol.  IV.   Electric  Lighting.     Photometry.  In  Press. 


HOLLAND.  The  Urine,  the  Gastric  Contents,  the  Common 
Poisons,  and  the  Milk.  Memoranda,  Chemical  and  Microscopi- 
cal, for  Laboratory  Use.  6th  Ed.  Illustrated  and  interleaved,  $1.00 

LEFFMANN.  Compend  of  Medical  Chemistry,  Inorganic 
a'nd  Organic.  4th  Edition,  Revised.  .80;  Interleaved,  ii.oo 

LEFFMANN.  Analysis  of  Milk  and  Milk  Products.  2d 
Edition,  Enlarged.  Illustrated.  tl-?5 

LEFFMANN.  Water  Analysis.  For  Sanitary  and  Technic  Pur- 
poses. Illustrated.  4th  Edition.  $1-25 

LEFFMANN.  Structural  Formulas.  Including  180  Structural 
and  Stereo-Chemical  Formulae.  i2mo.  Interleaved.  fi.oo 

LEFFMANN  AND  BEAM.  Select  Methods  in  Food  Analy- 
sis. Illustrated  Just  Ready.  $250 

MUTER.  Practical  and  Analytical  Chemistry.  2d  American 
from  the  Eighth  English  Edition.  Revised  to  meet  the  requirements 
of  American  Students.  56  Illustrations.  $1.25 

OETTEL.     Exercises  in  Electro-Chemistry.    Illustrated.        .75 

OETTEL.     Electro-Chemical  Experiments.    Illustrated.         .75 

RICHTER.  Inorganic  Chemistry,  sth  American  from  loth  Ger- 
man Edition.  Authorized  translation  by  EDGAR  F.  SMITH,  M.A., 
PH.D.  89  Illustrations  and  a  Colored  Plate.  $i-75 

RICHTER.  Organic  Chemistry.  3d  American  Edition.  Trans, 
from  the  Sth  German  by  EDGAR  F.  SMITH.  Illustrated,  a  Volumes. 
Vol.  I.  Aliphatic  Series.  625  Pages.  $3.00 

Vol.  II.  Carbocvclic  Series.  671  Pages.  $3.00 

ROCKWOOD.  Chemical  Analysis  for  Students  of  Medicine, 
Dentistry,  and  Pharmacy.  Illustrated.  Just  Ready. 

SMITH.     Electro-Chemical  Analysis.    2d  Ed.    28  Illus.       $1.25 

SMITH  AND  KELLER.  Experiments.  Arranged  for  Students 
in  General  Chemistry.  4th  Edition.  Illustrated.  .60 


SUBJECT  CATALOGUE. 


BUTTON.  Volumetric  Analysis.  A  Systematic  Handbook  for 
the  Quantitative  Estimation  of  Chemical  Substances  by  Measure, 
Applied  to  Liquids,  Solids,  and  Gases.  8th  Edition,  Revised.  112 
Illustrations.  $5.00 

SYMONDS.     Manual  of  Chemistry,  for  Medical   Students. 

2d  Edition.  $2.00 

TRAUBE.    Physico-Chemical  Methods.    Translated  by  Hardin. 

97  Illustrations.  $i-5o 

THRESH.    Water  and  Water  Supplies.    3d  Edition.          $2.00 

ULZER  AND  FRAENKEL.    Chemical  Technical  Analysis. 

Translated  by  Fleck.     Illustrated.  $1.25 

WOODY.    Essentials    of    Chemistry    and    Urinalysis.     4th 

Edition.     Illustrated.  #1.50 

V  Special  Catalogue  of  Books  on  Chemistry  free  upon  application. 

CHILDREN. 

CAUTLEY.    Feeding  of  Infants  and  Young  Children  by  Nat- 
ural and  Artificial  Methods.  $2.00 
HALE.    On  the  Management  of  Children.  .50 

HATFIELD.  Compend  of  Diseases  of  Children.  With  a 
Colored  Plate.  2d  Edition.  .80;  Interleaved,  $1.00 

IRELAND.     The  Mental  Affections  of  Children,    zd  Ed.    $4.00 

MEIGS.  Infant  Feeding  and  Milk  Analysis.  The  Examination 
of  Human  and  Cow's  Milk,  Cream,  Condensed  Milk,  etc.,  and 
Directions  as  to  the  Diet  of  Young  Infants.  .50 

POWER.  Surgical  Diseases  of  Children  and  their  Treat- 
ment by  Modern  Methods.  Illustrated.  $2.50 

SHUTTLEWORTH.  Mentally  Deficient  Children.  New 
Edition.  $1.50 

STARR.  The  Digestive  Organs  in  Childhood.  The  Diseases  of 
the  Digestive  Organs  in  Infancy  and  Childhood,  sd  Edition,  Rewrit- 
ten and  Enlarged.  Illustrated.  Just  Ready.  $3.00 

STARR.  Hygiene  of  the  Nursery.  Including  the  General  Regi- 
men and  Feeding  of  Infants  and  Children,  and  the  Domestic  Manage- 
ment of  the  Ordinary  Emergencies  of  Early  Life,  Massage,  etc.  6th 
Edition.  25  Illustrations.  $1.00 

SMITH.     Wasting  Diseases  of  Children.    6th  Edition.        $2.00 

TAYLOR  AND  WELLS.  The  Diseases  of  Children.  2d  Edi- 
tion, Revised  and  Enlarged.  Illustrated.  8vo.  Just  Ready.  $4.50 

DIAGNOSIS. 

BROWN.     Medical  Diagnosis.     A  Manual  of  Clinical   Methods. 

4th  Edition.     112  Illustrations.  Cloth,  $2.25 

DA  COSTA.     Clinical  Examination  of  the  Blood.    Illustrated. 

In  Press. 

EMERY.     Bacteriological  Diagnosis.  In  Press. 

MEMMINGER.   Diagnosis  by  the  Urine.   2d  Ed.   24  Illus.  $1.00 


MEDICAL   BOOKS. 


PERSHING.     Diagnosis   of  Nervous  and    Mental    Diseases. 

Illustrated.    Just  Ready.  $'-25 

STEELL.     Physical  Signs  of  Pulmonary  Disease.  $'-25 

TYSON.     Hnnd-Book  of  Physical  Diagnosis.     For  Students  and 

Physicians.     By  the  Professor  of  Clinical  Medicine  in  the  University 

of  Pennsylvania.      Illus.     4th  Ed..  Improved  anri  Enlarged.     With 

Two  Colored  and  55  other  Illustrations.    Just  Ready.  $i-5<> 


DENTISTRY. 

Special  Catalogue  of  Dental  Books  sent  free  upon  application. 

BARRETT.  Dental  Surgery  for  General  Practitioners  and 
Students  of  Medicine  and  Dentistry.  Extraction  of  Teeth, 
etc.  3d  Edition.  Illustrated.  fi.oo 

BROOMELL.  Anatomy  and  Histology  of  the  Human  Mouth 
and  Teeth.  284  Handsome  Illustrations.  $4-5<> 

FILLEBROWN.      A    Text-Book    of    Operative     Dentistry. 

Written  by  invitation  of  the  National  Association  of  Dental  Facul- 
ties.    Illustrated.  $2.25 

GORGAS.  Dental  Medicine.  A  Manual  of  Materia  Medica  and 
Therapeutics,  yth  Edition,  fust  Ready.  Cloth,  $4.00;  Sheep,  $5.00 

GORGAS.  Questions  and  Answers  for  the  Dental  Student. 
Embracing  all  the  subjects  in  the  Curriculum  of  the  Dental  Student. 
Octavo.  Just  Ready.  $6.00 

HARRIS.     Principles  and   Practice  of  Dentistry.     Including 

Anatomy,  Physiology,    Pathology,  Therapeutics,   Dental  Surgery, 

.  and  Mechanism,     isth  Edition.     Revised  by  F.  J.  S.  GORGAS,  M.D., 

D.D.S.     1250  Illustrations.  Cloth,  $6.00;  Leather,  $7.00 

HARRIS.  Dictionary  of  Dentistry.  Including  Definitions  of  Such 
Words  and  Phrases  of  the  Collateral  Sciences  as  Pertain  to  the  Art  and 
Practice  of  Dentistry.  6th  Edition.  Revised  and  Enlarged  by  FBR- 
DINAND  F.  S.  GORGAS,  M.D.,  D.D.S.  Cloth,  $5.00;  Leather,  f  6.00 

HEATH.  Injuries  and  Diseases  of  the  Jaws.  4th  Edition.  187 
Illustrations.  £4.50 

RICHARDSON.  Mechanical  Dentistry.  7th  Edition.  Thor- 
oughly Revised  and  Enlarged  by  DR.  GHO.  W.  WARREN.  691  Illus- 
trations. Cloth,  $5.00;  Leather,  $6.00 

SMITH.     Dental  Metallurgy.    Illustrated.  $1.75 

TAFT.     Index  of  Dental  Periodical  Literature.  $2.00 

TOMES.     Dental  Anatomy.    Human  and  Comparative.    263  Illus- 
trations.   $th  Edition.  $4.00 
TOMES.    Dental  Surgery.    4th  Edition.    289  Illustrations.     $4.00 

WARREN.  Compend  of  Dental  Pathology  and  Dental  Medi- 
cine. With  a  Chapter  on  Emergencies.  3d  Edition.  Illustrated. 

.80;  Interleaved,  $1.25 

WARREN.  Dental  Prosthesis  and  Metallurgy.  129  Ills.  $1.25 
WHITE.    The  Mouth  and  Teeth.     Illustrated.  .40 


SUBJECT  CATALOGUE. 


DICTIONARIES. 

GOULD.    The  Illustrated  Dictionary  of  Medicine,  Biology, 

and  Allied  Sciences.     Being  an  Exhaustive  Lexicon  of  Medicine 

and  those  Sciences  Collateral  to  it:    Biology  (Zoology  and  Botany), 

Chemistry,   Dentistry,  Parmacology,  Microscopy,  etc.,  with  many 

useful  Tables  and  numerous  fine  Illustrations.     1633  pages.     5th  Ed. 

Sheep  or  Half  Dark  Green  Leather,  $10.00;  Thumb  Index,  $11.00 

Half  Russia,  Thumb  Index,  $12.00 

GOULD.  The  Medical  Student's  Dictionary,  nth  Edition. 
Illustrated.  Including  all  the  Words  and  Phrases  Generally  Used 
inMedicine,  with  their  Proper  Pronunciation  and  Definition,  Based 
on  Recent  Medical  Literature.  With  a  new  Table  of  Eponymic 
Terms  and  Tests  and  Tables  of  the  Bacilli,  Micrococci,  Mineral 
Springs,  etc.,  of  the  Arteries,  Muscles,  Nerves,  Ganglia,  Plexuses,  etc. 
nth  Edition.  Enlarged  by  over  100  pages  and  illustrated  with  a 
large  number  of  engravings.  840  pages. 

Half  Green  Morocco,  $2.50;   Thumb  Index,  $3.00 

GOULD.  The  Pocket  Pronouncing  Medical  Lexicon.  4th  Edi- 
tion. (30,000  Medical  Words  Pronounced  and  Defined.)  Containing 
all  the  Words,  their  Definition  and  Pronunciation,  that  the  Medical, 
Dental,  or  Pharmaceutical  Student  Generally  Comes  in  Contact 
With ;  also  Elaborate  Tables  of  Eponymic  Terms.  Arteries,  Muscles, 
Nerves,  Bacilli,  etc.,  etc.,  a  Dose  List  in  both  English  and  Metric 
Systems,  etc.,  Arranged  in  a  Most  Convenient  Form  for  Reference  and 
Memorizing.  A  new  (Fourth)  Edition,  Revised  and  Enlarged. 
838  pages. 

Full  Limp  Leather,  Gilt  Edges,  $1.00  ;  Thumb  Index,  $1.25 
120,000  Copies  of  Gould's  Dictionaries  Have  Been  Sold. 

GOULD  AND  PYLE.  Cyclopedia  of  Practical  Medicine  and 
Surgery.  Seventy-two  Special  Contributors.  Illustrated. 
One  Volume.  A  Concise  Reference  Handbook,  Alphabetically 
Arranged,  of  Medicine,  Surgery,  Obstetrics,  Materia  Medica, 
Therapeutics,  and  the  Various  Specialties,  with  Particular  Reference 
to  Diagnosis  and  Treatment.  Compiled  under  the  Editorial  Super- 
vision of  GEORGE  M.  GOULD,  M.D.,  Author  of  "An  Illustrated 
Dictionary  of  Medicine"  •  Editor  "  Philadelphia  Medical  Journal," 
etc.;  and  WALTER  L.  PYLE,  M.D.,  Assistant  Surgeon  Wills  Eye 
Hospital  ;  formerly  Editor  "  International  Medical  Magazine,"  etc., 
and  Seventy-two  Special  Contributors.  With  many  Illustrations. 
Large  Square  8vo,  to  correspond  with  Gould's  "  Illustrated  Dic- 
tionary." Just  Ready.  Full  Sheep  or  Half  Dark-Green  Leather,  $10.00 
With  Thumb  Index,  $n.oo;  Ha  f  Russia,  Thumb  Index,  $12.00  net. 
%*  Sample  Pages  and  Illustrations  and  Descriptive  Circulars  of 

Gould's  Dictionaries  and  Cyclopedia  sent  free  upon  application. 

HARRIS.  Dictionary  of  Dentistry.  Including  Definitions  of  Such 
Words  and  Phrases  of  the  Collateral  Sciences  as  Pertain  to  the  Art 
and  Practice  of  Dentistry.  6th  Edition.  Revised  and  Enlarged  by 
FERDINAND  J.  S.  GORGAS,  M.D.,  D.D.S.  Cloth,  $5.00;  Leather,  $6  oo 

LONGLEY.  Pocket  Medical  Dictionary.  With  an  Appendix, 
containing  Poisons  and  their  Antidotes,  Abbreviations  used  in  Pre- 
scriptions, etc.  Cloth,  .75;  Tucks  and  Pocket,  $1.00 

MAXWELL,  Terminolpgia  Medica  Polyglotta.  By  Dr. 
THEODORE  MAXWELL,  Assisted  by  Others.  $3.00 

The  object  of  this  work  is  to  assist  the  medical  men  of  any  nationality 

In  reading   medical  literature  written   in  a  language  not   their  own. 

Each  term  is  usually  given  in  seven  languages,  viz. :  English,  French, 

German,  Italian,  Spanish,  Russian,  and  Latin. 

TREVES  AND  LANG.    German-English  Medical  Dictionary . 

Half  Russia,  $3.25 


MEDICAL  BOOKS. 


EAR  (see  also  Throat  and  Nose). 

BURNETT.     Hearing  and  How  to  Keep  It.    Illustrated.          .40 

DALBY.  Diseases  and  Injuries  of  the  Ear.  4th  Edition.  38 
Wood  Engravings  and  8  Colored  Plates.  $2.50 

HOVELL.  Diseases  of  the  Ear  and  Naso-Pharynx.  Includ- 
ing Anatomy  and  Physiology  of  the  Organ,  together  with  the  Treat- 
ment of  the  Affections  of  the  Nose  and  Pharynx  which  Conduce  to 
Aural  Disease.  128  Illustrations.  2d  Edition.  Just  Ready.  $5.50 

PRITCHARD.  Diseases  of  the  Ear.  3d  Edition,  Enlarged. 
Many  Illustrations  and  Formulae.  $1.50 


ELECTRICITY. 

BIGELOW.  Plain  Talks  on  Medical  Electricity  and  Bat- 
teries. With  a  Therapeutic  Index  and  a  Glossary.  43  Illustra- 
tions. 2d  Edition.  |i.oo 

HEDLEY.  Therapeutic  Electricity  and  Practical  Muscle 
Testing.  99  Illustrations.  $2.50 

JACOBY.  Electrotherapy.  2  Volumes.  Illustrated.  Including 
Special  Articles  by  Special  Authors.  Just  Ready. 

JONES.    Medical  Electricity.  3d  Edition.   117  Illus.  $3.00 


EYE. 

A  Special  Circular  of  Books  on  the  Eye  sent  free  upon  application. 

DONDERS.  The  Nature  and  Consequences  of  Anomalies  of 
Refraction.  With  Portrait  and  Illustrations.  Half  Morocco,  £i.  25 

PICK.  Diseases  of  the  Eye  and  Ophthalmoscopy.  Trans- 
lated by  A.  B.  HALK,  M.  D.  157  Illustrations,  many  of  which  are  in 
colors,  and  a  glossary.  Cloth,  $4.50  ;  Sheep,  $5.50 

GOULD  AND  PYLE.  Compend  of  Diseases  of  the  Eye  and 
Refraction.  Including  Treatment  and  Operations,  and  a  Section 
on  Local  Therapeutics.  With  Formulae,  Useful  Tables,  a  Glossary, 
and  in  Illus.,  several  of  which  are  in  colors.  2d  Edition,  Revised. 

Cloth,  .80  ;  Interleaved,  $1.00 

HARLAN.     Eyesight,  and  How  to  Care  for  It.     Illus.  .40 

HARTRIDGE.  Refraction.  104  Illustrations  and  Test  Types. 
nth  Edition,  Enlarged  fust  Ready. 


HARTRIDGE.      On  the  Ophthalmoscope.    4th  Edition.    With 
4  Colored  Plates  and  68  Wood-cuts,    fust  Ready.  $1.50 

HANSELL  AND  REBER.     Muscular  Anomalies  of  the  Eye. 
Illustrated.  $1.50 

HANSELL  AND  BELL.      Clinical  Ophthalmology.    Colored 
Plate  of  Normal  Fundus  and  120  Illustrations.  $1.50 


10  SUBJECT  CATALOGUE. 

MORTON.  Refraction  of  the  Eye.  Its  Diagnosis  and  the  Cor- 
rection of  its  Errors.  6th  Edition.  $1.00 

OHLEMANN.  Ocular  Therapeutics.  Authorized  Translation, 
and  Edited  by  DR.  CHARLES  A.  OLIVER.  $1.75 

PHILLIPS.  Spectacles  and  Eyeglasses.  Their  Prescription 
and  Adjustment.  2d  Edition.  49  Illustrations.  $1.00 

SWANZY.  Diseases  of  the  Eye  and  Their  Treatment,  7th 
Edition,  Revised  and  Enlarged.  164  Illustrations,  i  Plain  Plate, 
and  a  Zephyr  Test  Card.  $2.50 

THORINGTON.  Retinoscopy.  4th  Edition.  Carefully  Revised. 
Illustrated.  Just  Ready.  $1.00 

THORINGTON.  Refraction  and  How  to  Refract.  200  Illustra- 
tions, 13  of  which  are  Colored.  2d  Edition.  $1.50 

WALKER.  Students'  Aid  in  Ophthalmology.  Colored  Plate 
and  40  other  Illustrations  and  Glossary.  $i-5° 

WRIGHT.  Ophthalmology.  2d  Edition,  Revised  and  Enlarged. 
117  Illustrations  and  a  Glossary.  Just  Ready.  $3.00 

FEVERS. 

GOODALL  AND  WASHBOURN.  Fevers  and  Their  Treat- 
ment. Illustrated.  $3.00 

GOUT  AND  RHEUMATISM. 

DUCKWORTH.  A  Treatise  on  Gout.  With  Chromo-lithographs 
and  Engravings.  Cloth,  $6.00 

HAIG.  Causation  of  Disease  by  Uric  Acid.  A  Contribution  to 
the  Pathology  of  High  Arterial  Tension.  Headache,  Epilepsy,  Gout, 
Rheumatism,  Diabetes,  etc.  5th  Edition.  $3 .00 

HEART. 

THORNE.  The  Schott  Methods  of  the  Treatment  of  Chronic 
Heart  Disease.  Third  Edition.  Illustrated.  #1.75 

HISTOLOGY. 

GUSHING.     Compend  of  Histology.     By  H.  H.  GUSHING,  M.D., 

Demonstrator  of  Histology,  Jefferson  Medical  College,  Philadelphia. 
Illustrated.    Nearly  Ready.  .80;  Interleaved,  $1.00 

STIRLING.  Outlines  of  Practical  Histology.  368  Illustrations. 
2d  Edition,  Revised  and  Enlarged.  With  new  Illustrations.  $2.00 

STOHR,  Histology  and  Microscopical  Anatomy.  Edited  by 
A.  SCHAPBR,  M.D.,  University  of  Breslau,  formerly  Demonstrator  of 
Histology,  Harvard  Medical  School.  Fourth  American  from  gth  Ger- 
man Edition,  Revised  and  Enlarged.  379  Illus.  Just  Ready.  $3.00 


MEDICAL  BOOKS. 


HYGIENE  AND  WATER  ANALYSIS. 

Special  Catalogue  of  Books  on  Hygiene  sent  free  upon  application  . 

C  ANFIELD.  Hygiene  of  the  Sick-Room.  A  Book  for  Nurses 
and  Others.  Being  a  Brief  Consideration  of  Asepsis,  Antisepsis,  Dis- 
infection, Bacteriology,  Immunity,  Heating,  Ventilation,  etc.  $1.25 

CONN.     Agricultural  Bacteriology.     Illus.   Just  Ready.     $2.50 

COPLIN.     Practical  Hygiene.     A  Complete  American  Text-Book. 

138  Illustrations.  New  Edition.  Preparing. 

HARTSHORNE.  Our  Homes.  Illustrated.  .40 

KENWOOD.  Public  Health  Laboratory  Work.  116  Illustra- 

tions and  3  Plates.  $2.00 

LEFFMANN.  Select  Methods  in  Food  Analysis.  53  Illustra- 

tions and  4  Plates.  Just  Ready.  $2.50 

LEFFMANN.  Examination  of  Water  for  Sanitary  and 

Technical  Purposes.  4th  Edition.  Illustrated.  $l-*5 

LEFFMANN.  Analysis  of  Milk  and  Milk  Products.  Illus- 

trated. Second  Edition.  $1-25 

LINCOLN.  School  and  Industrial  Hygiene.  .40 

McFARLAND.  Prophylaxis  and  Personal  Hygiene.  In  Press. 

NOTTER.  The  Theory  and  Practice  of  Hygiene.  15  Plates 
and  138  other  Illustrations.  8vo.  2d  Edition.  £7.00 

PARKES.  Hygiene  and  Public  Health.  By  Louis  C.  Parkes, 
M.D.  6th  Edition.  Enlarged.  Illustrated.  Just  Ready.  $3.00 

PARKES.  Popular  Hygiene.  The  Elements  of  Health.  A  Book 
for  Lay  Readers.  Illustrated.  $1-^5 

STARR.  The  Hygiene  of  the  Nursery.  Including  the  General 
Regimen  and  Feeding  of  Infants  and  Children,  and  the  Domestic 
Management  of  the  Ordinary  Emergencies  of  Early  Life,  Massage, 
etc.  6th  Edition.  25  Illustrations.  $1.00 

STEVENSON  AND  MURPHY.  A  Treatise  on  Hygiene.  By 
Various  Authors,  in  Three  Octave  Volumes.  Illustrated. 

Vol.  I,  $6.00;  Vol.  II,  $6.00;  Vol.  Ill,  $5.00 
%*  Each  Volume  sold  separately.   Special  Circular  upon  application. 

THRESH.     Water  and  Water  Supplies.    3d  Edition.          $2.00 

WILSON.     Hand-Book    of  Hygiene  and   Sanitary    Science. 

Wiih  Illustrations.     8th  Edition. 


WEYL.     Sanitary  Relations  of  the  Coal-Tar  Colors.    Author- 
ized Translation  by  HENRY  LEFFMANN,  M.D.,  PH.D.  $1.25 


LUNGS  AND  PLEURAE. 

KNOPF.      Pulmonary  Tuberculosis.      Its   Modern  Prophylaxis 
and  Treatment  in  Special  Institutions* and  at  Home.     Illus.        $3-Oo 

STEELL.     Physical  Signs  of  Pulmonary  Disease.   Illus.  $1.25 


12  SUBJECT  CATALOGUE. 

MASSAGE— PHYSICAL  EXERCISE. 

OSTROM.  Massage  and  the  Original  Swedish  Move- 
ments. Their  Application  to  Various  Diseases  of  the  Body.  A 
Manual  for  Students,  Nurses,  and  Physicians.  Fourth  Edition,  En- 
larged. 105  Illustrations,  many  of  which  are  original.  $1.00 

MITCHELL  AND  GULICK.  Mechanotherapy.  Illus.  InPress. 
TREVES.     Physical  Education.     Methods,  etc.  .75 

WARD.     Notes  on  Massage.     Interleaved.          Paper  cover,  $1.00 


MATERIA    MEDICA    AND     THERA- 
PEUTICS. 

BIDDLE.  Materia  Medica  and  Therapeutics.  Including  Dose 
List,  Dietary  for  the  Sick,  Table  of  Parasites,  and  Memoranda  of 
New  Remedies,  isth  Edition,  Revised.  64  Illustrations  and  a 
Clinical  Index.  Cloth,  $4.00;  Sheep,  $5.00 

BRACKEN.     Outlines  of  Materia  Medica  and  Pharmacology.    $2.75 

COBLENTZ.  The  Newer  Remedies.  Including  their  Synonyms, 
Sources,  Methods  of  Preparation,  Tests,  Solubilities,  Doses,  etc. 
3d  Edition,  Enlarged  and  Revised.  $1.00 

COHEN.  Physiologic  Therapeutics.  Mechanotherapy,  Mental 
Theiapeutics,  Electrotherapy.  Climatology,  Hydrotherapy,  Pneu- 
matothetapy,  Prophylaxis,  Dietetics,  etc.  n  Volumes.  Octavo. 
Illustrated.  5  Volumes  now  ready. 

Special  Descriptive  Circular  ivill  be  sent  upon  application. 
DAVIS.    Materia  Medica  and  Prescription  Writing.        $1.50 

GORGAS.  Dental  Medicine.  A  Manual  of  Materia  Medica  and 
Therapeutics,  jth  Edition,  Revised,  fust  Ready.  t4-°° 

GROFF.  Materia  Medica  for  Nurses,  with  questions  for  Self  Exam- 
ination and  a  complete  Glossary.  Ji-zs 

HELLER.  Essentials  of  Materia  Medica,  Pharmacy,  and 
Prescription  Writing.  $1.50 

MAYS.    Theine  in  the  Treatment  of  Neuralgia.     %  bound,  .50 

POTTER.  Hand-Book  of  Materia  Medica,  Pharmacy,  and 
Therapeutics,  including  the  Action  of  Medicines,  Special  Therapeu- 
tics, Pharmacology,  etc.,  including  over  600  Prescriptions  and  For- 
mulae. 8th  Edition,  Revised  and  Enlarged.  With  Thumb  Index  in 
each  copy.  Just  Ready.  Cloth,  $5.00;  Sheep,  $6.00 

POTTER.  Compend  of  Materia  Medica,  Therapeutics,  and 
Prescription  Writing,  with  Special  Reference  to  the  Physiologi- 
cal Action  of  Drugs.  6th  Edition.  .80;  Interleaved,  $1.00 

MURRAY.     Rough  Notes  on  Remedies.     4th  Edition.         $1.25 


MEDICAL  BOOKS.  13 


SAYRE.  Organic  Materia  Medica  and  Pharmacognosy.  An 
Introduction  to  the  Study  of  the  Vegetable  Kingdom  and  the  Vege- 
table and  Animal  Drugs.  Comprising  the  Botanical  and  Physical 
Characteristics,  Source,  Constituents,  and  Pharmacopeial  Prepara- 
tions, Insects  Injurious  to  Drugs,  and  Pharmacal  Botany.  With 
sections  on  Histology  and  Microtechnique,  by  W.  C.  STEVENS. 
374  Illustrations,  many  of  which  are  original.  2d  Edition. 

Cloth,  $4.50 

TAVERA.     Medicinal  Plants  of  the  Philippines,    fust  Ready. 

$2.00 

WHITE  AND  WILCOX.  Materia  Medica,  Pharmacy,  Phar- 
macology, and  Therapeutics,  sth  American  Edition,  Revised  by 
REYNOLD  W.  WILCOX,  M.A.,  M.D.,  LL.D.,  Professor  of  Clinical 
Medicine  and  Therapeutics  at  the  New  York  Post-Graduate  Medical 
School.  Just  Ready.  Cloth,  $3.00;  Leather,  $3.50 

"  The  care  with  which  Dr.  Wilcox  has  performed  his  work  is  con- 
spicuous on  every  page,  and  it  is  evident  that  no  recent  drug  possess- 
ing any  merit  has  escaped  his  eye.  We  believe,  on  the  whole,  this  is 
the  best  book  on  Materia  Medica  and  Therapeutics  to  place  in  the 
hands  of  students,  and  the  practitioner  will  find  it  a  most  satisfactory 
work  for  daily  use." — The  Cleveland  Medical  Gazette. 


MEDICAL    JURISPRUDENCE     AND 
TOXICOLOGY. 

REESE.   Medical  Jurisprudence  and  Toxicology.  A  Text-Book 

for  Medical  and   Legal   Practitioners   and  Students.     $th   Edition. 
Revised  by  HENRY  LEFFMANN,  M.D.       do. ,$3.00;  Leather,  $3.50 

"  To  the  student  of  medical  jurisprudence  and  toxicology  it  is  in- 
valuable, as  it  is  concise,  clear,  and  thorough  in  every  respect." — The 
American  Journal  of  the  Medical  Sciences. 

MANN.     Forensic  Medicine  and  Toxicology.     Illus.          $6.50 

TANNER.     Memoranda  of  Poisons.    Their  Antidotes  and  Tests. 
Sth  Edition,  by  DR  HENRY  LBFFMANN.    Just  Ready.  .75 


MICROSCOPY. 

CARPENTER.  The  Microscope  and  Its  Revelations.  Sth 
Edition,  Revised  and  Enlarged  817  Illustrations  and  23  Plates. 
Just  Ready.  Cloth,  $8.co ;  Half  Morocco,  $9.00 

LEE.  The  Microtomist's  Vade  Mecum.  A  Hand-Book  of 
Methods  of  Microscopical  Anatomy.  887  Articles.  5th  Edition, 
Enlarged.  $4.00 

REEVES.  Medical  Microscopy,  including  Chapters  on  Bacteri- 
ology, Neoplasms,  Urinary  Examination,  etc.  Numerous  Illus- 
trations, some  of  which  are  printed  in  colors.  $z-5° 

WETHER  ED.  Medical  Microscopy.  A  Guide  to  the  Use  of  the 
Microscope  in  Practical  Medicine.  100  Illustrations.  $2.00 


14  SUBJECT  CATALOGUE. 

MISCELLANEOUS. 

BERRY.     Diseases  of  Thyroid  Gland.    Illustrated.  $4.00 

BURNETT.     Foods  and  Dietaries.    A  Manual  of  Clinical  Diet- 

etics.    2d  Edition. 


BUXTON.  Anesthetics.  Illustrated.  3d  Edition.  £1.50 

COHEN.  Organotherapy.  /»  Press. 

DAVIS.  Dietotherapy.  Food  in  Health  and  Disease.  In  Press. 
GOULD.  Borderland  Studies.  Miscellaneous  Addresses  and 

Essays.  12010.  $2.00 

GREENE.  Medical  Examination  for  Life  Insurance.  Illus- 

trated. $4.00 

HAIG.  Causation  of  Disease  by  Uric  Acid.  The  Pathology  of 

High  Arterial  Tension,  Headache,  Epilepsy,  Gout,    Rheumatism, 

Diabetes,  Bright's  Disease,  etc.  sthEdition.  $3.00 

HAIG.  Diet  and  Food.  Considered  in  Relation  to  Strength  and 

Power  of  Endurance.  3d  Edition.  Just  Ready.  $1.00 

HEMMETER.  Diseases  of  the  Stomach.  Their  Special  Path- 

ology, Diagnosis,  and  Treatment.     With  Sections  on  Anatomy,  Diet- 

etics, Surgery,  etc.  2d  Edition,  Revised  and  Enlarged.  Illustrated. 

Cloth,  $6.00;  Sheep,  $7.00 
HEMMETER.  Diseases  of  the  Intestines.  Illustrated.  2  Vol- 

umes. 8vo.  Just  Ready.  |io  oo 

HENRY.  A  Practical  Treatise  on  Anemia.  Hall  Cloth,  .50 
LEFFMANN.  Food  Analysis.  Illustrated.  Just  Ready.  £2.50 
NEW  SYDENHAM  SOCIETY'S  PUBLICATIONS.  Circulars 

upon  application.  Per  Annum,  $8.00 

OSGOOD.  The  Winter  and  Its  Dangers.  .40 

OSLER  AND  McCRAE.  Cancer  of  the  Stomach.  #2.00 

PACKARD.  Sea  Air  and  Sea  Bathing.  .40 

RICHARDSON.  Long  Life  and  How  to  Reach  It.  .40 

ST.  CLAIR.  Medical  Latin.  $1.00 

TISSIER.  Pneumatotherapy.  In  Press. 

TURNBULL.  Artificial  Anesthesia.  4th  Edition.  Illus.  $2.50 
WEBER  AND  HINSDALE.  Climatology.  2  Vols.  Illustrated 

with  Maps.  Just  Ready. 

WILSON.  The  Summer  and  Its  Diseases.  .40 

WINTERNITZ.  Hydrotherapy.  Illustrated.  In  Press. 


NERVOUS  DISEASES. 

DERCUM.    Rest,  Hypnotism,  Mental  Therapeutics.    InPress. 

GORDINIER.  The  Gross  and  Minute  Anatomy  of  the  Cen- 
tral Nervous  System.  With  271  original  Colored  and  other 
Illustrations.  Cloth,  $6.00;  Sheep,  $7.00 

GOWERS.    Manual  of  Diseases  of  the  Nervous  System.    A 
Complete  Text-Book.     Revised,  Enlarged,  and  in  many  parts  Re- 
written.    With  many  new  Illustrations.     Two  volumes. 
Vol.  I.   Diseases  of  the  Nerves  and  Spinal  Cord,     sd  Edition,  En- 
larged. Cloth,  $4.00;  Sheep,  $5.00 
Vol.  II.    Diseases  of    the  Brain  and  Cranial  Nerves ;   General  and 
Functional  Disease.    2d  Edition.              Cloth,  $4.00 ;  Sheep,  $5.00 

GOWERS.    Syphilis  and  the  Nervous  System.  £1.00 


MEDICAL  BOOKS.  15 


GO  WERS.  Clinical  Lectures.  A  New  Volume  of  Essays  on  the 
Diagnosis,  Treatment,  etc.,  of  Diseases  of  the  Nervous  System.  $2.00 

GOWERS.   Epilepsy  and  Other  Chronic  Convulsive  Diseases. 

2d  Edition.  Just  Ready.  $3.00 

HORSLEY.  The  Brain  and  Spinal  Cord.  The  Structure  and 

Functions  of.  Numerous  Illustrations.  $*-5Q 

ORMEROD.  Diseases  of  the  Nervous  System.  66  Wood  En- 

gravings. $1.00 

OSLER.  Chorea  and  Choreiform  Affections.  £2.00 

PERSHING.  Diagnosis  of  Nervous  and  Mental  Diseases. 

Illustrated.  Just  Ready.  $1.25 

PRESTON.  Hysteria  and  Certain  Allied  Conditions.  Their 

Nature  and  Treatment.    Illustrated.  $2.00 

WOOD.    Brain  Work  and  Overwork.  .40 

NURSING  (see  also  Massage). 

Special  Catalogue  of  Books  for  Nurses  sent  fret  upon  application. 

CAN  FIELD.  Hygiene  of  the  Sick-Room.  A  Book  for  Nurses  and 
Others.  Being  a  Brief  Consideration  of  Asepsis,  Antisepsis,  Disinfec- 
tion, Bacteriology,  Immunity,  Heating  and  Ventilation,  and  Kindred 
Subjects  for  the  Use  of  Nurses  and  Other  Intelligent  Women.  $1.25 

CUFF.    Lectures  to  Nurses  on  Medicine.    Third  Edition.    $1.25 

DOMVILLE.    Manual  for  Nurses  and  Others  Engaged  in  At- 
tending the  Sick,   gth  Edition.  With  Recipes  for  Sick-room  Cook- 
.  ery,  etc.  In  Press. 

FULLERTON.    Obstetric  Nursing.    41  Ills.    5th  Ed.         fi.oo 
FULLERTON.     Surgical    Nursing.    3d  Ed.    69  Ills.          $1.00 

GROFF.  Materia  Medica  for  Nurses.  With  Questions  for  Self-Ex- 
amination  and  a  very  complete  Glossary.  $1.25 

"  It  will  undoubtedly  prove  a  valuable  aid  to  the  nurse  in  securing  a 

knowledge  of   drugs  and  their  uses.''  —  The  Medical  Record,  New 


HUMPHREY.     A    Manual    for     Nurses.      Including    General 

Anatomy  and   Physiology,  Management  of  the  Sick  Room,    etc. 

23d  Edition.    79  Illustrations.  £1.00 

"  In  the  fullest  sense,  Dr.  Humphrey's  book  is  a  distinct  advance  on 

all  previous   manuals.     It  is,  in  point  of  fact,  a  concise  treatise  on 

medicine  and  surgery  for  the  beginner,  incorporating  with  the  text  the 

management  of  childbed  and  the  hygiene  of  the  sick-room.     Its  value 

is  greatly  enhanced  by  copious  wood-cuts  and  diagrams  of  the  bones 

and  internal  organs."  —  British  Medical  Journal  ,  London. 

STARR.  The  Hygiene  of  the  Nursery.  Including  the  General 
Regimen  and  Feeding  of  Infants  and  Children,  and  the  Domestic  Man- 
agement of  the  Ordinary  Emergencies  of  Early  Life,  Massage,  etc.  6th 
Edition.  25  Illustrations.  £1.00 

TEMPERATURE  AND  CLINICAL  CHARTS.    See  page  6. 

VOSWINKEL.  Surgical  Nursing.  Second  Edition,  Enlarged. 
112  Illustrations.  fi.oo 


16  SUBJECT  CATALOGUE. 

OBSTETRICS. 

CAZEAUX  AND  TARNIER.  Midwifery.  With  Appendix  by 
MuNDfc.  The  Theory  and  Practice  of  Obstetrics,  including  the  Dis- 
eases ol  Pregnancy  and  Parturition,  Obstetrical  Operations,  etc. 
8th  Edition.  Illustrated  by  Colored  and  other  full-page  Plates,  and 
numerous  Wood  Engravings.  Cloth,  $4.50  ;  Full  Leather,  $5.50 

EDGAR.     Text-Book  of  Obstetrics.     Illustrated.       Preparing. 

FULLERTON.    Obstetric  Nursing,     sth  Ed.    Illustrated.    $1.00 

LANDIS.  Compend  of  Obstetrics.  7th  Edition,  Revised  by  WM. 
H.  WELLS,  Demonstrator  of  Clinical  Obstetrics,  Jefferson  Medical 
College.  52  Illustrations.  Just  Ready.  .80;  Interleaved,  $1.00 

WINCKEL.  Text-Book  of  Obstetrics,  Including  the  Pathol- 
ogy and  Therapeutics  of  the  Puerperal  State.  Authorized 
Translation  by  J.  CLIFTON  EDGAR,  M.D.  Illus.  Cloth,  $5.00 

PATHOLOGY. 

BARLOW.    General  Pathology.     795  pages.    8vo.  $5.00 

BLACK.     Micro-Organisms.     The  Formation  of  Poisons.  .75 

BLACKBURN.  Autopsies.  A  Manual  of  Autopsies  Designed  for 
the  Use  of  Hospitals  for  the  Insane  and  other  Public  Institutions. 
Ten  full-page  Plates  and  other  Illustrations.  $1-25 

CONN.    Agricultural  Bacteriology.     Illus.   Just  Ready.      $2.50 
COPLIN.  Manual  of  Pathology.  Including  Bacteriology,  Technic 
of  Post-Mortems,  Methods  of  Pathologic  Research,  etc.     330  Illus- 
trations, 7  Colored  Plates.     3d  Edition.  $3-5<> 
DA  COSTA.    Clinical  Pathology  of  the  Blood.    Illus.    In  Press. 
EMERY.     Bacteriological  Diagnosis.                                In  Press. 
HEWLETT.     Manual  of  Bacteriology.    75  Illustrations.    $3.00 
ROBERTS.  Gynecological  Pathology.   Illus.  Just  Ready    $0.00 
THAYER.       Compend    of    General    Pathology.       Illustrated. 
Nearly  Ready.     .80  ;  Interleaved,  JU.co 
THAYER.     Compend  of  Special  Pathology.     Illustrated. 

Nearly  Ready.     .80;  Interleaved,  $1.00 

VIRCHOW.     Post-Mortem  Examinations.    3d  Edition.         .75 
WHITACRE.     Laboratory  Text-Book  of   Pathology.     With 
121  Illustrations.  $1.50 

WILLIAMS.  Bacteriology.  A  Manual  for  Students.  90  Illus- 
trations. 2d  Edition,  Revised.  Just  Ready.  $i-5° 

PHARMACY. 

Special  Catalogue  of  Books  on  Pharmacy  sent  free  upon  application. 

COBLENTZ.  Manual  of  Pharmacy.  A  Complete  Text-Book 
by  the  Professor  in  the  New  York  College  of  Pharmacy,  ad  Edition, 
Revised  and  Enlarged.  437  Illus.  Cloth,  $3. 50;  Sheep,  $4- 5° 

COBLENTZ.    Volumetric  Analysis.    Illustrated.  In  Press. 

BEASLEY.  Book  of  3100  Prescriptions.  Collected  from  the 
Practice  of  the  Most  Eminent  Physicians  and  Surgeons — English, 
French,  and  American.  A  Compendious  History  of  the  Materia 
Medica,  Lists  of  the  Doses  of  all  the  Officinal  and  Established  Pre- 
parations, an  Ladex  of  Diseases  and  their  Remedies.  7th  Ed.  $2.00 


MEDICAL  BOOKS.  17 

BEASLEY.  Druggists'  General  Receipt  Book.  Comprising 
a  Copious  Veterinary  Formulary,  Recipes  in  Patent  and  Proprietary 
Medicines,  Druggists'  Nostrums,  etc. ;  Perfumery  and  Cosmetics, 
Beverages,  Dietetic  Articles  and  Condiments,  Trade  Chemicals, 
Scientific  Processes,  and  many  Useful  Tables.  loth  Ed.  $2.00 

BEASLEY.  Pharmaceutical  Formulary.  A  Synopsis  of  the 
British,  French,  German,  and  United  States  Pharmacopoeias.  Com- 
prising Standard  and  Approved  Formulae  for  the  Preparations  and 
Compounds  Employed  in  Medicine.  1 2th  Edition.  $2.00 

PROCTOR.  Practical  Pharmacy.  3d  Edition,  with  Illustrations 
and  Elaborate  Tables  oi  Chemical  Solubilities,  etc.  .  $3.00 

ROBINSON.     Latin  Grammar  of  Pharmacy  and   Medicine. 

3d  Edition.     With  elaborate  Vocabularies.  $1 .75 

SAYRE.    Organic  Materia  Medica  and  Pharmacognosy.    An 

Introduction  to  the  Study  of  the  Vegetable  Kingdom  and  the  Vege- 
table and  Animal  Drugs.  Comprising  the  Botanical  and  Physical 
Characteristics,  Source,  Constituents,  and  Pharmacopeial  Prepar- 
ations, Insects  Injurious  to  Drugs,  and  Parmacal  Botany.  With 
sections  on  Histology  and  Microtechnique,  by  W.  C.  STEVENS. 
374  Illustrations.  Second  Edition.  Cloth,  14.50 

SCOVILLE.  The  Art  of  Compounding.  Second  Edition,  Re- 
vised and  Enlarged.  Cloth,  $2.50 

STEWART.  Compend  of  Pharmacy.  Based  upon  "  Reming- 
ton's Text-Book  of  Pharmacy."  sth  Edition,  Revised  in  Accord- 
ance with  the  U.  S.  Pharmacopoeia,  1890.  Complete  Tables  of 
Metric  and  English  Weights  and  Measures.  .80;  Interleaved,  $1.00 

TAVERA.     Medicinal  Plants  of  the  Philippines.    Just  Ready . 

$2.00 

UNITED  STATES  PHARMACOPOEIA.  7th  Decennial  Revision. 
Cloth,  £2.50  (postpaid,  $2.77)  ;  Sheep,  13.00  (postpaid,  $3.27) ;  Inter- 
leaved, *4.oo  (postpaid.  $4.50);  Printed  on  one  side  of  page  only, 
unbound,  $3.50  (postpaid,  $3.90). 

Select  Tables  from  the  U.  S.  P.     Being  Nine  of  the  Most  Impor- 
tant and  Useful  Tables,  Printed  on  Separate  Sheets.  .25 

POTTER.  Hand-Book  of  Materia  Medica,  Pharmacy,  and 
Therapeutics.  600  Prescriptions.  Sth  Ed.  Clo.,  fc.oo;  Sh.,  $6.00 


PHYSIOLOGY. 

BIRCH.  Practical  Physiology.  An  Elementary  Class  Book. 
62  Illustrations.  $i-75 

BRUBAKER.  Compend  of  Physiology.  loth  Edition,  Revised 
and  Enlarged.  Illustrated.  .80;  Interleaved,  $1.00 

JONES.  Outlines  of  Physiology.  96  Illustrations.    Nearly  Ready 

KIRKES.  Handbook  of  Physiology.  i7th  Authorized  Edition. 
Revised,  Rearranged,  and  Enlarged.  By  PROP.  W.  D.  HALLIBUR- 
TON, of  Kings  College.  London.  681  Illustrations,  some  of  which 
are  in  colors.  Just  Ready.  Cloth,  $3.00;  Leather,  $3.75 


18  SUBJECT  CATALOGUE. 


LANDOIS.  A  Text-Book  of  Human  Physiology,  Including 
Histology  and  Microscopical  Anatomy,  with  Special  Reference  to 
the  Requirements  of  Practical  Medicine,  sth  American,  translated 
from  the  gth  German  Edition,  with  Additions  by  WM.  STIRLING, 
M.D.,D.SC.  845  Illus.,  many  of  which  are  printed  in  colors.  In  Press. 

STARLING.     Elements  of  Human  Physiology.    loollls.    $1.00 

STIRLING.  Outlines  of  Practical  Physiology.  Including 
Chemical  and  Experimental  Physiology,  with  Special  Reference  to 
Practical  Medicine,  sd  Edition.  289  Illustrations.  $2.00 

TYSON.    Cell  Doctrine.    Its  History  and  Present  State.        $1.50 

PRACTICE. 

BEALE.  On  Slight  Ailments;  their  Nature  and  Treatment. 
2d  Edition,  Enlarged  and  Illustrated.  II-2S 

FAGGE.  Practice  of  Medicine.  4th  Edition,  by  P.  H.  PYE- 
SMITH,  M.D.  2  Volumes.  In  Press. 

FOWLER.  Dictionary  of  Practical  Medicine.  By  various 
writers.  An  Encyclopaedia  of  Medicine.  Clo.,$3.oo;  Half  Mor.  $4.00 

GOULD  AND  PYLE.  Cyclopedia  of  Practical  Medicine  and 
Surgery.  A  Concise  Reference  Handbook,  Alphabetically 
Arranged,  with  particular  Reference  to  Diagnosis  and  Treatment. 
Edited  by  DRS.  GOULD  and  PYLE,  Assisted  by  72  Special  Con- 
tributors. Illustrated,  one  volume.  Large  Square  Octavo,  Uniform 
with  "Gould's  Illustrated  Dictionary." 

Sheep  or  Half  Morocco,  $10.00;  with  Thumb  Index,  $11.00 
Half  Russia,  Thumb  Index,  $12.00 

JKJ=-  Complete  descriptive  circular  free  upon  application. 

HUGHES.  Compend  of  the  Practice  of  Medicine.  6th  Edition, 
Revised  and  Enlarged. 

Part  I.  Continued,  Eruptive,  and  Periodical  Fevers,  Diseases  of  the 
Stomach,  Intestines,  Peritoneum,  Biliary  Passages,  Liver,  Kid- 
neys, etc.,  and  General  Diseases,  etc. 

Part  II.  Diseases  of  the  Respiratory  System,  Circulatory  System, 
and  Nervous  System;  Diseases  of  the  Blood,  etc. 

Price  of  each  part,  .80;  Interleaved,  Ji.oo 

Physician's   Edition.      In  one  volume,  including  the  above  two 

parts,  a  Section  on  Skin   Diseases,  and  an  Index.     6th  Revised 

Edition.     625  pp.  Full  Morocco,  Gilt  Edge,  $2.25 

MURRAY.     Rough  Notes  on  Remedies.    4th  Ed.    Just  Ready. 

$1.25 

TAYLOR.  Practice  of  Medicine.  6th  Edition.  Just  Ready.  JS4.oo 
TYSON.  The  Practice  of  Medicine.  By  JAMES  TYSON,  M.D., 
Professor  of  Medicine  in  the  University  of  Pennsylvania.  A  Com- 
plete Systematic  Text-book  with  Special  Reference  to  Diagnosis  and 
Treatment.  2d  Edition,  Enlarged  and  Revised.  Colored  Plates  and 
125  other  Illustrations.  1222  Pages.  Cloth,  $5.50;  Leather,  $6.50 

PRESCRIPTION  BOOKS. 

BEASLEY.  Book  of  3100  Prescriptions.  Collected  from  the 
Practice  of  the  Most  Eminent  Physicians  and  Surgeons — English, 
French,  and  American.  A  Compendious  History  of  the  Materia, 
Medica,  Lists  of  the  Doses  of  all  Officinal  and  Established  Prepara- 
tions, and  an  Index  of  Diseases  and  their  Remedies.  7th  Ed.  $2.00 


MEDICAL  BOOKS.  1» 


BEASLEY.  Druggists'  General  Receipt  Book.  Comprising 
a  Copious  Veterinary  Formulary,  Recipes  in  Patent  and  Proprie- 
tary Medicines,  Druggists'  Nostrums,  etc.  ;  Perfumery  and  Cos- 
metics, Beverages,  Dietetic  Articles  and  Condiments,  Trade  Chem- 
icals, Scientific  Processes,  and  an  Appendix  of  Useful  Tables, 
roth  Edition,  Revised.  $2.00 

BEASLEY.  Pocket  Formulary.  A  Synopsis  of  the  British,  French, 
German,  and  United  States  Pharmacopoeias  and  the  chief  unofficial 
Formularies.  iath  Edition.  $2.00 


SKIN. 

BULKLEY.    The  Skin  in  Health  and  Disease.    Illustrated.    .40 
CROCKER.    Diseases  of  the  Skin.    Their  Description,  Pathol- 
ogy, Diagnosis,  and  Treatment,  with  Special  Reference  to  the  Skin 
Eruptions  of  Children.   92  Illus.   $d  Edition.  Preparing. 

SCHAMBERG.  Diseases  of  the  Skin.  2d  Edition,  Revised  and 
Enlarged.  105  Illustrations.  Being  No.  16  ?Quiz-Compend?  Series. 

Cloth,  .80;  Interleaved,  $1.00 

VAN  HARLINGEN.  On  Skin  Diseases.  A  Practical  Manual 
of  Diagnosis  and  Treatment,  with  special  reference  to  Differential 
Diagnosis.  3d  Edition,  Revised  and  Enlarged.  With  Formulae 
and  60  Illustrations,  some  of  which  are  printed  in  colors.  $2.75 

SURGERY  AND  SURGICAL  DIS- 
EASES (see  also  Urinary  Organs). 

BERRY.  Diseases  of  the  Thyroid  Gland  and  Their  Surgical 
Treatment.  Illustrated.  Just  Ready.  $4.00 

BUTLIN.  Operative  Surgery  of  Malignant  Disease.  2d  Edi- 
tion. Illustrated.  Octavo.  $4-5° 

DEAVER.  Surgical  Anatomy.  A  Treatise  on  Human  Anatomy 
in  its  Application  to  Medicine  and  Surgery.  With  about  400  very 
Handsome  full-page  Illustrations  Engraved  from  Original  Drawings 
made  by  special  Artists  from  Dissections  prepared  for  the  purpose. 
Three  Volumes.  Royal  Square  Octavo. 

Cloth,  $21.00;  Half  Morocco  or  Sheep,  $24.00  ;  Half  Russia,  $27.00 
Complete  descriptive  circular  and  special  terms  upon  application. 

DEAVER.  Appendicitis,  Its  Symptoms,  Diagnosis,  Pathol- 
ogy, Treatment,  and  Complications.  Elaborately  Illustrated 
with  Colored  Plates  and  other  Illustrations.  2d  Edition.  13-5° 

DULLES.  What  to  Do  First  in  Accidents  and  Poisoning. 
5th  Edition.  New  Illustrations.  $1.00 

FULLERTON.     Surgical  Nursing,     sd  Edition.    69  Illus.    $i  oo 
HAMILTON.    Lectures  on  Tumors.    3d  Edition.  $1.25 

HEATH.   Minor  Surgery  and  Bandaging.   i2th  Edition,  Revised 
and  Enlarged.   195  Illus.,  Formulae,  Diet  List,  etc.  Just  Ready.  $i.;o 
HEATH.    Injuries  and  Diseases  of  the  Jaws.    4th  Ed.      $4.50 
HORWITZ.    Compend  of  Surgery  and  Bandaging,  including 
Minor  Surgery,  Amputations,  Fractures,  Dislocations,  Surgical  Dis- 
eases, and  the  Latest  Antiseptic  Rules,  etc.,  with  Differential  Diagno- 
sis  and   Treatment.     $th   Edition,  very  much  Enlarged  and  Rear- 
ranged.   167  Illustrations,  98  Formulae.   Clo.,  .80;  Interleaved,  $1.00 


SUBJECT  CATALOGUE. 


JACOBSON.  Operations  of  Surgery.  Over  zoo  Illustrations. 

Cloth,  $3.00 ;  Leather,  $4.00 

KEHR.  Gall-Stone  Disease.  Translated  by  WILLIAM  WOTKYNS 
SEYMOUR,  M.D.  Just  Ready.  $2.50 

LANE.    Surgery  of  the  Head  and  Neck,     no  Illus.  $5.00 

MACREADY.  A  Treatise  on  Ruptures.  24  Full-page  Litho- 
graphed Plates  and  Numerous  Wood  Engravings.  Cloth,  $6.00 

MAKINS.  Surgical  Experiences  in  South  Africa.  1899-1900. 
Illustrated.  Just  Ready.  $4.00 

MAYLARD.  Surgery  of  the  Alimentary  Canal.  97  Illustrations, 
zd  Edition,  Revised.  $3.00 

MOULLIN.  Text-Book  of  Surgery.  With  Special  Reference  to 
Treatment,  sd  American  Edition.  Revised  and  edited  by  JOHN  B. 
HAMILTON,  M.D.,  LL.D.,  Professor  of  the  Principles  of  Surgery  and 
Clinical  Surgery,  Rush  Medical  College,  Chicago.  623  Illustrations, 
many  of  which  are  printed  in  colors.  Cloth,  $6.00;  Leather,  $7.00 

SMITH.  Abdominal  Surgery.  Being  a  Systematic  Description  of 
all  the  Principal  Operations.  224  Illus.  6th  Ed.  2  Vols.  Clo.,  $10.00 

VOSWINKEL.  Surgical  Nursing.  Second  Edition,  Revised  and 
Enlarged,  in  Illustrations.  $1.00 

WALSHAM.  Manual  of  Practical  Surgery.  7th  Ed.,  Re- 
vised and  Enlarged.  483  Engravings.  950  pages.  $3-5° 

TEMPERATURE  CHARTS,   ETC. 

GRIFFITH.  Graphic  Clinical  Chart  for  Recording  Temper- 
ature, Respiration,  Pulse,  Day  of  Disease,  Date,  Age,  Sex, 
Occupation,  Name,  etc.  Printed  in  three  colors.  Sample  copies 
free.  Put  up  in  loose  packages  of  fifty,  .50.  Price  to  Hospitals,  500 
copies,  $4.00 ;  1000  copies,  $7.50.  With  name  of  Hospital  printed 
on.  50  cts.  extra. 

KEEN'S  CLINICAL  CHARTS.  Seven  Outline  Drawings  of  the 
Body,  on  which  may  be  marked  the  Course  of  Disease,  Fractures, 
Operations,  etc.  Each  Drawing  may  be  had  separately,  twenty-five 
to  pad.  25  cents. 

SCHREINER.  Diet  Lists.  Arranged  in  the  form  of  a  chart. 
With  Pamphlets  of  Specimen  Dietaries.  Pads  of  50.  .75 

THROAT  AND    NOSE   (see  also  Ear). 

COHEN.    The  Throat  and  Voice.     Illustrated.  .40 

HALL.  Diseases  of  the  Nose  and  Throat,  zd  Edition,  Enlarged. 
Two  Colored  Plates  and  80  Illustrations.  Just  Ready.  $2-75 

HOLLOPETER.     Hay  Fever.     Its  Successful  Treatment.      $1.00 

KNIGHT.  Diseases  of  the  Throat.  A  Manual  for  Students. 
Illustrated.  Nearly  Ready. 

LAKE.  Laryngeal  Phthisis,  or  Consumption  of  the  Throat. 
Colored  Illustrations.  Just  Ready.  $z  oo 

MACKENZIE.  Pharmacopoeia  of  the  London  Hospital  for 
Dis.  of  the  Throat,  sth  Ed.,  Revised  by  Dr.  F.  G.  HARVEY.  $1.00 

McBRIDE.  Diseases  of  the  Throat,  Nose,  and  Ear.  With  col- 
ored Illustrations  from  original  drawings.  3d  Edition.  $7.00 

POTTER.  Speech  and  its  Defects.  Considered  Physiologically, 
Pathologically,  and  Remedially.  $1.00 

SHEILD.     Nasal  Obstructions.     Illustrated.    Just  Ready.    $1.50 

URINE  AND  URINARY  ORGANS, 

ACTON.  The  Functions  and  Disorders  of  the  Reproductive 
Organs  in  Childhood,  Youth,  Adult  Age,  and  Advanced  Life, 
Considered  in  their  Physiological,  Social,  and  Moral  Relations. 
Sth  Edition.  $1.75 


MEDICAL  BOOKS.  21 


BEALE.  One  Hundred  Urinary  Deposits.  On  eight  sheets, 
for  the  Hospital,  Laboratory,  or  Surgery.  Paper,  $2.00 

HOLLAND.  The  Urine,  the  Gastric  Contents,  the  Common 
Poisons,  and  the  Milk.  Memoranda,  Chemical  and  Microscopi- 
cal, for  Laboratory  Use.  Illustrated  and  Interleaved.  6th  Ed.  £1.00 

KLEEN.     Diabetes  and  Glycosuria.  $2.50 

MEMMINGER.    Diagnosis  by  the  Urine,   zd  Ed.  24  Illus.  |i.oo 

MORRIS.  Renal  Surgery,  with  Special  Reference  to  Stone  in  the 
Kidney  and  Ureter  and  to  the  Surgical  Treatment  of  Calculous 
Anuria.  Illustrated.  $2.00. 

MOULLIN.  Enlargement  of  the  Prostate.  Its  Treatment  and 
Radical  Cure.  2 d  Edition.  Illustrated.  $1.75 

MOULLIN.  Inflammation  of  the  Bladder  and  Urinary  Fever. 
Octavo.  $1.50 

SCOTT.  The  Urine.  Its  Clinical  and  Microscopical  Examination. 
41  Lithographic  Plates  and  other  Illustrations.  Quarto.  Cloth,  $5.00 

TYSON.  Guide  to  Examination  of  the  Urine.  For  the  Use  of 
Physicians  and  Students.  With  Colored  Plate  and  Numerous  Illus- 
trations engraved  on  wood,  gth  Edition,  Revised.  tI-y5 

VAN   NUYS.    Chemical  Analysis  of  Urine.    39  Illus.         fi.oo 


VENEREAL  DISEASES. 

GOWERS.    Syphilis  and  the  Nervous  System.  $t.oo 

STURGIS   AND   CABOT.      Student's    Manual    of  Venereal 

Diseases.   7th  Revised  and  Enlarged  Ed     i2mo.  Just  Ready.  $1.25 


VETERINARY. 

BALLOU.    Veterinary  Anatomy  and  Physiology.    29  Graphic 
Illustrations.  .80;  Interleaved,  Ji.oo 


WOMEN,  DISEASES  OF. 

BISHOP.     Uterine  Fibromyomata.   Their  Pathology,  Diagnosis, 
and  Treatment.     Illustrated.    Just  Ready.  Cloth,  £3  50 

BYFORD   (H.  T.).    Manual   of  Gynecology.    Second   Edition, 
Revised  and  Enlarged  by  100  pages.     341  Illustrations.  f3-oo 

DUHRSSEN.     A  Manual   of  Gynecological    Practice.     105 
Illustrations.  I1- 5° 

FULLERTON.     Surgical   Nursing.     3d   Edition,   Revised  and 
Enlarged.     69  Illustrations.  $1.00 

LEWERS.    Diseases  of  Women.    146  Illus.    sth  Ed.  $2.50 

MONTGOMERY.     Practical    Gynecology.     A  Complete  Sys- 
tematic Text- Book.    527  Illustrations.    Cloth,  $5.00;  Leather,  $6.00 

ROBERTS.     Gynecological  Pathology.    With  many  Handsome 
Illustrations.  Just  Ready. 

WELLS.    Compend  of  Gynecology.    Illustrated.    2d  Edition. 

.80 ;  Interleaved,  |i  .00 


22  SUBJECT  CATALOGUE. 

COMPENDS. 


From,  The  Southern  Clinic. 

"  We  know  of  no  series  of  books  issued  by  any  house  that  so  fully 
meets  our  approval  as  these  ?Quiz-Compends?.  They  are  well  ar- 
ranged, full,  and  concise,  and  are  really  the  best  line  of  text-books  that 
could  be  found  for  either  student  or  practitioner." 


BLAKISTON'S  ?QUIZ-COMPENDS? 

The  Best  Series  of  Manuals  for  the  Use  of  Students. 
Price  of  each,  Cloth,  .80.         Interleaved,  for  taking  Notes,  $1.00. 

4^-  These  Compends  are  based  on  the  most  popular  text-books 
and  the  lectures  of  prominent  professors,  and  are  kept  constantly  re- 
vised, so  that  they  may  thoroughly  represent  the  present  state  of  the 
subjects  upon  which  they  treat. 

JJES"-  The  authors  have  had  large  experience  as  Quiz-Masters  and 
attaches  of  colleges,  and  are  well  acquainted  with  the  wants  of  students. 

J^-  They  are  arranged  in  the  most  approved  .form,  thorough  and 
concise,  containing  over  600  fine  illustrations,  inserted  wherever  they 
could  be  used  to  advantage. 

4®-  Can  be  used  by  students  of  any  college. 

4£S~  They  contain  information  nowhere  else  collected  in  such  a 
condensed,  practical  shape.  Illustrated  Circular  free. 

No.  i.  POTTER.  HUMAN  ANATOMY.  Sixth  Revised  and 
Enlarged  Edition.  Including  Visceral  Anatomy.  Can  be  used 
with  either  Morris's  or  Gray's  Anatomy.  117  Illustrations  and  16 
Lithographic  Plates  of  Nerves  and  Arteries,  with  Explanatory 
Tables,  etc.  By  SAMUEL  O.  L.  POTTER,  M.D.,  Professor  of  the 
Practice  of  Medicine,  College  of  Physicians  and  Surgeons,  San 
Francisco  ;  Brigade  Surgeon,  U.  S.  Vol. 

No.  2.  HUGHES.  PRACTICE  OF  MEDICINE.  Part  I.  Sixth 
Edition,  Enlarged  and  Improved.  By  DANIEL  E.  HUGHES,  M.D., 
Physician-in-Chief,  Philadelphia  Hospital,  late  Demonstrator  of 
Clinical  Medicine,  Jefferson  Medical  College,  Phila. 

No.  3.  HUGHES.  PRACTICE  OF  MEDICINE.  Part  II. 
Sixth  Edition,  Revised  and  Improved.  Same  author  as  No.  2. 

No.  4.  BRUBAKER.  PHYSIOLOGY.  Tenth  Edition,  with 
Illustrations  and  a  table  of  Physiological  Constants.  Enlarged 
and  Revised.  By  A.  P.  BRUBAKER,  M.D.,  Professor  of  Physiology 
and  General  Pathology  in  the  Pennsylvania  College  of  Dental 
Surgery;  Adjunct  Professor  of  Physiology,  Jefferson  Medical 
College,  Philadelphia,  etc. 

No.  5.  LANDIS.  OBSTETRICS.  Seventh  Edition.  By  HENRY  G. 
LANDIS,  M.D.  Revised  and  Edited  by  WM.  H.  WELLS,  M.D., 
Demonstrator  of  Clinical  Obstetrics,  Jefferson  Medical  College, 
Philadelphia.  Enlarged.  52  Illustrations. 

No.  6.  POTTER.  MATERIA  MEDICA,  THERAPEUTICS, 
AND  PRESCRIPTION  WRITING.  Sixth  Revised  Edition 
(U.  S.  P.  1890).  By  SAMUEL  O.  L.  POTTER,  M.D.,  Professor  of 
Practice,  College  of  Physicians  and  Surgeons,  San  Francisco; 
Brigade  Surgeon,  U.  S.  Vol. 


MEDICAL  BOOKS. 


PQUIZ-COMPENDS  ?— Continued. 

No.  7.  WELLS.  QYNECOLOGY.  Second  Edition.  By  WM.  H. 
WKLLS,  M.D.,  Demonstrator  of  Clinical  Obstetrics,  Jefferson 
Medical  College,  Philadelphia.  140  Illustrations. 

No.  8.  GOULD  AND  PYLE.  DISEASES  OF  THE  EYE 
AND  REFRACTION.  Second  Edition.  Including  Treatment 
and  Surgery,  and  a  Section  on  Local  Therapeutics.  By  GEORGE 
M.  GOULD,  M.D.,  and  W.  L.  PYLB,  M.D.  With  Formulae,  Glossary 
Tables,  and  109  Illustrations,  several  of  which  are  Colored. 

No.  9.  HORWITZ.  SURGERY,  Minor  Surgery,  and  Bandag- 
ing. Fifth  Edition,  Enlarged  and  Improved.  By  ORVILLB 
HORWITZ,  B.  s-,  M.D.,  Clinical  Professor  of  Genito-Urinary  Surgery 
and  Venereal  Diseases  in  Jefferson  Medical  College ;  Surgeon  to 
Philadelphia  Hospital,  etc.  With  98  Formulae  and  71  Illustrations. 

No.  10.  LEFFMANN.  MEDICAL  CHEMISTRY.  Fourth 
Edition.  Including  Urinalysis,  Animal  Chemistry,  Chemistry  of 
Milk,  Blood,  Tissues,  the  Secretions,  etc.  By  HENRY  LEFFMANN, 
M.D.,  Professor  of  Chemistry  in  the  Woman  s  Medical  College  of 
Penna  ;  Pathological  Chemist,  Jefferson  Medical  College  Hospital. 

No.  II.  STEWART.  PHARMACY.  Fifth  Edition.  Based  upon 
Prof.  Remington's  Text-Book  of  Pharmacy.  By  F.  E.  STEWART, 
M.D.,  PH. G..  late  Quiz-Master  in  Pharmacy  and  Chemistry,  Phila- 
delphia College  of  Pharmacy ;  Lecturer  at  Jefferson  Medical 
College.  Carefully  revised  in  accordance  with  the  new  U.  S.  P. 

No.  12.  BALLOU.  VETERINARY  ANATOMY  AND  PHY- 
SIOLOGY. Illustrated.  By  WM.  R.  BALLOU,  M.D.,  Professor 
of  Equine  Anatomy  at  New  York  College  of  Veterinary  Surgeons ; 
Physician  to  Bellevue  Dispensary,  etc.  29  graphic  Illustrations 

No.  13.  WARREN.  DENTAL  PATHOLOGY  AND  DEN- 
TAL MEDICINE.  Third  Edition  Illustrated.  Containing 
a  Section  on  Emergencies.  By  GEO.  W.  WARREN,  D.D.S.,  Chiet 
of  Clinical  Staff,  Pennsylvania  College  of  Dental  Surgery. 

No.  14.  HATFIELD.  DISEASES  OF  CHILDREN.  Second 
Edition.  Colored  Plate.  By  MARCUS  P.  HATFIBLD,  Profes- 
sor of  Diseases  of  Children,  Chicago  Medical  College. 

No.  15.  THAYER.  GENERAL  PATHOLOGY.  By  A.  E. 
THAYER,  M.D. .Cornell  University  Medical  College.  Illustrated. 

No.  16.  SCHAMBERG.  DISEASES  OF  THE  SKIN.  Second 
Edition.  By  JAY  F.  SCHAMBERG,  M.D.,  Professor  of  Diseases  of 
the  Skin,  Philadelphia  Polyclinic.  Second  Edition,  Revised  and 


Edition.     By  JAY  F.  SCHAMBERG,  M.D.,  Professor  of  Diseases  of 
the  Skin,  Philadelphia  Polyclinic.    Se 
Enlarged.     105  handsome  Illustrations. 

No.  17.  GUSHING.  HISTOLOGY.  By  H.  H.  GUSHING,  M.D., 
Demonstrator  of  Histology,  Jefferson  Medical  College,  Philadel- 
phia. Illustrated. 

No.  18.  THAYER.  SPECIAL  PATHOLOGY.  Illustrated.  By 
same  Author  as  No.  15. 

Price,  each.  Cloth,  .80.  Interleaved,  for  taking  Notes,  $1.00. 

Careful  attention  has  been  given  to  the  construction  of  each  sentence, 
and  while  the  books  will  be  found  to  contain  an  immense  amount  of 
knowledge  in  small  space,  they  will  likewise  be  found  easy  reading ; 
there  is  no  stilted  repetition  of  words  ;  the  style  is  clear,  lucid,  and  dis- 
tinct. The  arrangement  of  subjects  is  systematic  and  thorough  ;  there 
is  a  reason  for  every  word.  They  contain  over  600  illustrations. 


THE  STANDARD  TEXT-BOOK 

MORRIS'  ANATOMY 

SECOND  EDITION 

Rewritten,    Revised.    Improved 

WITH  MANY  NEW  ILLUSTRATIONS 


Has  been  recommended  as  a  text-book  at  more  than 
seventy  of  the  most  prominent  medical  schools  in  the  United 
States  and  Canada,  and  is  considered  by  all  anatomists  as  a 
standard  authority.  It  contains  many  features  of  special 
advantage  to  students.  A  complete  Text-book.  Edited  by 
HENRY  MORRIS,  F.R.C.S.,  Surgeon  to,  and  Lecturer  on 
Anatomy  at,  Middlesex  Hospital,  assisted  by  J.  BLAND 

SUTTON,  F.R.C.S.,  J.   H.   DAVIES-COLLEY,   F.R.C.S.,  WM.  J. 

WALSHAM,  F.R.C.S.,  H.  ST.  JOHN  BROOKS,  M.D.,  R.  MAR- 
CUS GUNN,  F.R.C.S.,  ARTHUR  HENSMAN,  F.R.C.S.,  FRED- 
ERICK TREVES,  F.R.C.S.,  WILLIAM  ANDERSON,  F.R.C.S., 
PROF.  W.  H.  A.  JACOBSON,  and  ARTHUR  ROBINSON,  M.R.C.S. 

Octavo.     With  790  Illustrations,  of  which  a  large  number 
are  printed  in  colors 

CLOTH.  $6.00;    LEATHER,  $7.00 


"The  ever-growing  popularity  of  the  book  with  teach- 
ers and  students  is  an  index  of  its  value,  and  it  may  safely 
be  recommended  to  all  interested." — From  The  Medical 
Record,  New  York. 

"  Of  all  the  text-books  of  moderate  size  on  human 
anatomy  in  the  English  language,  Morris  is  undoubtedly 
the  most  up-to-date  and  accurate." — From  The  Philadel- 
phia Medical  Journal. 

THUMB  INDEX  IN  EACH  COPY 


f30m-6/ii] 


Pood  analysis 


Sept  4  1912 Piatrafes 


Y£  V3638 


